Radio communication station, radio communication method, and radio communication program

Abstract

To provide a radio station for performing communication using a plurality of frequency bands simultaneously, where weakened radio field intensity of a radio access point is early detected and treated to reduce power consumption while securing communication stability.SOLUTION: A radio communication system 1 comprises a radio communication station including: a communication unit for performing communication using a plurality of frequency bands simultaneously; and a control unit comprising a PS (Power Save) execution unit, a TWT (Target Wake Time) execution unit, and a schedule generation unit. The PS execution unit performs switching to a PS state for each frequency. The TWT execution unit performs switching between a normal state and a TWT stand-by state for each frequency. The schedule generation unit generates a schedule. In the schedule generated by the schedule generation unit, setting is performed so that at least one frequency band is in the normal state in each time band and the PS state is made in at least one time during the normal states.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention mainly relates to a wireless communication station that connects to a wireless access point and performs wireless communication. [Background technology]

[0002] Patent Document 1 discloses a communication system that performs communication using TWT (Target Wake Time), which is a function that reduces power consumption by switching a wireless station between wake-up and standby modes according to a predetermined schedule.

[0003] Patent Document 2 discloses a wireless communication device that can suppress the influence of interference between links in MLO (Multi-Link Operation). MLO is a function that allows multiple frequency bands to be used simultaneously when connected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-33321 [Patent Document 2] Japanese Patent Publication No. 2022-61316 Summary of the Invention [Problem to be solved by the invention]

[0005] A wireless station that is in standby mode using a TWT cannot grasp the signal strength of the wireless access point to which it is connected. Therefore, the signal strength of the wireless access point to which it is connected may weaken while the wireless station is in standby mode. In this case, after returning from standby mode, the wireless station must try to connect to the wireless access point again, and therefore cannot immediately start communication. On the other hand, if the wireless station is kept active at all times, power consumption increases.

[0006] In a wireless communication system that is composed of at least one wireless access point and wireless stations that can use MLO, improved throughput can be expected even when the communication capacity within the system increases, but the simultaneous use of multiple frequency bands increases power consumption compared to wireless communication that uses a single frequency band. For example, in a wireless communication system that uses MLO in a school, conference room, event venue, etc., when all students in a school class access the same video, everyone can enjoy a comfortable experience with minimal communication delay, but in situations where MLO is not always necessary, it is desirable for multiple wireless stations to appropriately determine and control their own status, thereby reducing power consumption of the entire wireless communication system.

[0007] The present invention has been made in view of the above circumstances, and its main object is to provide a configuration for a wireless station that communicates simultaneously using multiple frequency bands, in which a weakening of the radio wave strength of a wireless access point is detected early and an appropriate countermeasure is taken, thereby ensuring communication stability while reducing power consumption.

[0008] The problem to be solved by the present invention is as described above. Next, the means for solving this problem and the effects thereof will be explained.

[0009] According to a first aspect of the present invention, there is provided a wireless communication station having the following configuration. Specifically, the wireless communication station connects to a wireless access point and performs wireless communication. The wireless communication station includes a communication unit and a control unit. The communication unit communicates using multiple frequency bands simultaneously. The control unit controls the communication unit. The control unit includes a PS execution unit, a TWT execution unit, and a schedule generation unit. The PS execution unit uses PS (Power Save) to switch, for each frequency band, to a PS state in which the wireless communication function is put to sleep and the state is resumed from sleep every time a recovery signal is received from the wireless access point. The TWT execution unit uses TWT (Target Wake Time) to switch, for each frequency band, between a normal state in which the wireless communication function is enabled and a TWT standby state in which the wireless communication function is disabled and signals including the recovery signal are not accepted. The schedule generation unit generates a schedule that determines, for each frequency band, whether the PS state is enabled and whether either the normal state or the TWT standby state is enabled. In the schedule generated by the schedule generating unit, at least one of the frequency bands is set to be in the normal state in each time period and to be in the PS state at least temporarily during the normal state.

[0010] This allows at least one frequency band to be in normal operation during each time period, enabling early detection of weakening of the signal strength of a wireless access point. As a result, the device can roam to a more appropriate wireless access point and quickly reconnect, ensuring communication stability (more specifically, shortening the period of communication outages). Furthermore, although there is a trade-off between communication stability and power consumption, power consumption can be reduced by setting the device to enter PS mode at least temporarily during normal operation.

[0011] The wireless communication station is preferably configured as follows: the schedule generation unit repeatedly applies a generated schedule element of a finite time length, and the total length of time during which the normal state is achieved in the schedule element differs between at least two of the frequency bands.

[0012] This allows the length of time during which the normal state is maintained to vary depending on the characteristics of the frequency band, making it possible to create a wireless communication environment that meets the needs of the user.

[0013] In the wireless communication station, it is preferable that in the schedule element, the total length of time during which the normal state is in the highest frequency band among the plurality of frequency bands is longer than the total length of time during which the normal state is in any one of the frequency bands other than the highest frequency band.

[0014] This allows the connection status with a wireless access point to be determined primarily using communication in the highest frequency band (in other words, the frequency band with the shortest communication distance), making it easier to maintain a state in which communication is possible using all frequency bands simultaneously.

[0015] The wireless communication station preferably has the following configuration: the communication unit has a function of communicating simultaneously using the 2.4 GHz band, the 5 GHz band, and the 6 GHz band, and in the schedule element, the total length of time during which the normal state is in the 6 GHz band is longer than the total length of time during which the normal state is in the 2.4 GHz band and longer than the total length of time during which the normal state is in the 5 GHz band.

[0016] Because the communication distance in the 6 GHz band is shorter than that of the other two frequency bands, if proper communication with a wireless access point is possible in the 6 GHz band, it is highly likely that proper communication will also be possible in the other two frequency bands. Therefore, by determining the connection status with a wireless access point primarily using communication in the 6 GHz band, it becomes easier to maintain a state in which communication is possible using all frequency bands simultaneously.

[0017] In the wireless communication station, it is preferable that the schedule generated by the schedule generating unit is set so that at least one of the frequency bands is in the PS state in each time period.

[0018] This allows the PS state to be used effectively, further reducing power consumption.

[0019] The wireless communication station preferably has the following configuration: the communication unit has a function of communicating using the three frequency bands simultaneously, and the schedule generated by the schedule generation unit is set so that, in each time period, two of the frequency bands are in the TWT standby state and the remaining frequency band is in the PS state.

[0020] This allows the TWT standby state and PS state to be used effectively, further reducing power consumption.

[0021] The wireless communication station preferably has the following configuration: the control unit includes a communication adjustment unit that reduces power consumption for communication by reducing at least one of the number of streams and bandwidth used for communication with the wireless access point, and the communication adjustment unit reduces power consumption for communication for the frequency band that is in the PS state.

[0022] This allows power consumption to be further reduced.

[0023] In the wireless communication station, when the control unit determines that the radio wave strength of the wireless access point in one of the multiple frequency bands in which the communication unit can communicate has fallen below a threshold, it is preferable that the control unit controls the communication unit to connect to a new wireless access point, regardless of the radio wave strength of the wireless access point in the other frequency bands.

[0024] This makes it easier to maintain a state in which communication using multiple frequency bands can be carried out simultaneously.

[0025] According to a second aspect of the present invention, there is provided a wireless communication method as follows. The wireless communication method uses a wireless communication station that connects to a wireless access point and communicates wirelessly. The wireless communication station is capable of communicating using multiple frequency bands simultaneously. The wireless communication station uses PS (Power Save) to switch, for each frequency band, to a PS state in which the wireless communication function is put to sleep and the station is restored from sleep whenever a recovery signal is received from the wireless access point. The wireless communication station uses TWT (Target Wake Time) to switch between a normal state in which the wireless communication function is enabled and a TWT standby state in which the wireless communication function is disabled and signals including the recovery signal are not accepted. The wireless communication method includes a schedule generation step and a state switching step. The schedule generation step generates a schedule that determines, for each frequency band, whether the PS state is enabled and which of the normal state and the TWT standby state is enabled. The state switching step switches, for each frequency band, whether the PS state is enabled and which of the normal state and the TWT standby state is enabled based on the schedule generated in the schedule generation step.

[0026] According to a third aspect of the present invention, there is provided a wireless communication program. The wireless communication program causes a wireless communication station that connects to a wireless access point and performs wireless communication to execute the following steps. The wireless communication station is capable of communicating using multiple frequency bands simultaneously. The wireless communication station uses PS (Power Save) to switch to a PS state in which the wireless communication function is put into sleep mode for each frequency band and is restored from sleep mode every time a return signal is received from the wireless access point. The wireless communication station uses TWT (Target Wake Time) to switch between a normal state in which the wireless communication function is enabled and a TWT standby state in which the wireless communication function is disabled and signals including the return signal are not accepted. The wireless communication program causes the wireless communication station to execute a schedule generation step and a state switching step. The schedule generation step generates a schedule that determines, for each frequency band, whether the PS state is enabled and whether either the normal state or the TWT standby state is enabled. In the state switching step, based on the schedule generated in the schedule generation step, it is determined whether the PS state is enabled and whether the normal state or the TWT standby state is enabled for each frequency band. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a block diagram of a wireless communication system. [Figure 2] 4 is a timing chart showing schedule elements according to the first embodiment. [Figure 3] FIG. 2 is a sequence diagram of the first embodiment. [Figure 4] 10 is a timing chart showing schedule elements according to the second embodiment. [Figure 5] FIG. 10 is a sequence diagram of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0028] Next, an embodiment of the present invention will be described with reference to the drawings. First, an overview of a wireless communication system 1 will be described with reference to FIG.

[0029] The wireless communication system 1 is installed in a facility such as a factory, warehouse, or office. The wireless communication system 1 is made up of multiple wireless communication devices, and a wireless communication network is constructed by the wireless communication devices communicating with each other wirelessly. The wireless communication system 1 includes a management device 10, multiple wireless access points 20, and a wireless station 30.

[0030] The management device 10 manages the wireless communication system 1. The management device 10 is, for example, a PC or a server device, and has a communication function and a calculation function. When the purpose of installing the wireless communication system 1 is to collect data within a facility, the management device 10 receives and manages data obtained via the wireless station 30 and the wireless access point 20. When the purpose of installing the wireless communication system 1 is to generate commands for devices within the facility, the management device 10 generates commands based on the received data and transmits the commands to the target devices.

[0031] The wireless access point 20 includes a wired communication module for communicating with the management device 10 and a wireless communication module for communicating with the wireless station 30. The wireless access point 20 uses the wireless communication module to establish a wireless LAN network and communicates wirelessly with one or more surrounding wireless stations 30. The wireless communication standard may be, for example, IEEE802.11, but is not limited to this.

[0032] The wireless station 30 communicates wirelessly with one of the surrounding wireless access points 20 via a wireless LAN network established by the wireless access point 20. The wireless communication standard may be, but is not limited to, IEEE802.11, which is the same as that of the wireless access point 20. The wireless communication system 1 may include one or more wireless stations 30.

[0033] The wireless access point 20 and the wireless station 30 support MLO, PS, and TWT. The wireless station 30 can use a power saving function to reduce power consumption related to communication by reducing at least one of the number of streams and bandwidth used in communication with the wireless access point 20. MLO, PS, and TWT will be described below.

[0034] MLO is an abbreviation for Multi-Link Operation. MLO is a technology for wireless communication using multiple frequency bands simultaneously. The wireless access point 20 and the wireless station 30 are compatible with the 2.4 GHz band, the 5 GHz band, and the 6 GHz band, and therefore can perform wireless communication using these three frequency bands simultaneously. Note that compatibility with the 6 GHz band is not essential, and the wireless access point 20 or the wireless station 30 may be compatible with only the 2.4 GHz band and the 5 GHz band, for example.

[0035] PS is an abbreviation for Power Save. PS is a technology that reduces power consumption by intermittently waking the wireless station 30 from sleep mode. Specifically, by enabling PS, the wireless station 30 puts its wireless communication function into sleep mode. Note that even during sleep mode, the wireless station 30 continues to receive specific signals (e.g., a return signal, described later) such as beacons from the wireless access point 20. The wireless access point 20 also transmits a return signal to the wireless station 30 at predetermined time intervals to wake up the wireless station 30. In this embodiment, the return signal is a signal included in a beacon, such as a Delivery Traffic Indication Message (DTIM) signal that notifies the wireless station 30 that there is data to transmit. Note that the return signal to wake up the wireless station 30 may be a signal other than the DTIM signal. Furthermore, whether or not the wireless station 30 is in the PS mode can be individually set for each frequency band. When the wireless station 30 receives a return signal, it enters an active state for a certain period of time, during which its wireless communication function is enabled. Therefore, in the PS mode, it is possible to detect the radio wave intensity of the wireless access point 20 to which it is connected.

[0036] TWT is an abbreviation for Target Wake Time. TWT is a technology that reduces power consumption by shortening the period during which the wireless station 30 is active. In the following description, the state in which the wireless communication function of the wireless station 30 is active is referred to as the "normal state," and the state in which the wireless station 30 is in sleep mode with only minimum functions enabled and cannot immediately perform wireless communication is referred to as the "TWT standby state." Unlike the sleep state in PS, the TWT standby state does not receive beacons transmitted by the wireless access point 20, and therefore the radio wave intensity of the connected wireless access point 20 cannot be detected. Generally, TWT determines a schedule that determines whether the wireless station 30 is in the normal state or the TWT standby state, and transmits the schedule to the wireless access point 20. The wireless station 30 switches between the normal state and the TWT standby state according to the schedule. Furthermore, the normal state and the TWT standby state can be individually set for each frequency band. As a result, the period during which the wireless station 30 is active is shortened, thereby reducing power consumption.

[0037] As shown in FIG. 1, the wireless station 30 includes a communication unit 31 and a control unit 32.

[0038] The communication unit 31 includes a wireless communication module. The communication unit 31 connects to the wireless access point 20 via the wireless LAN network and performs wireless communication with the wireless access point 20.

[0039] The control unit 32 includes a calculation device such as a CPU and a storage device such as an HDD, SSD, or flash memory. The calculation device performs various controls related to the wireless station 30 by executing programs stored in the storage device. For example, a wireless communication method is realized by the calculation device executing a wireless communication program. The storage device also stores control data necessary for control. Cooperation between the calculation device and the storage device enables the control unit 32 to function as a PS execution unit 32a, a TWT execution unit 32b, a schedule generation unit 32c, and a communication adjustment unit 32d. These names are given to the respective functions that the control unit 32 can realize.

[0040] The PS execution unit 32a switches the radio station 30 to a PS state or cancels the PS state for each frequency band by using the PS described above. The TWT execution unit 32b switches the radio station 30 to a normal state or switches the radio station 30 to a TWT standby state for each frequency band by using the TWT described above. The schedule generation unit 32c generates a schedule that determines whether to enable the PS state and whether to enable the normal state or the TWT standby state for each frequency band. The communication adjustment unit 32d reduces the number of streams and / or the bandwidth used in communication with the wireless access point 20 as necessary to reduce power required for communication. Note that the communication adjustment unit 32d is not an essential component and can be omitted.

[0041] 1, the wireless station 30 is mounted on a dolly 40 and is mobile. Therefore, the wireless communication environment around the wireless station 30 changes over time. As a result, as the wireless station 30 moves, the radio wave strength of the currently connected wireless access point 20 may decrease, making it impossible to perform appropriate wireless communication. In this case, the wireless station 30 roams and connects to a new wireless access point 20.

[0042] Here, the issues involved in using TWT will be described. While the wireless station 30 is in the TWT standby state, it cannot ascertain the radio wave strength of the wireless access point 20 to which it is connected. Therefore, for example, if the wireless station 30 is in the TWT standby state in all frequency bands, it cannot ascertain the radio wave strength of the wireless access point 20 until it switches to the normal state. Therefore, if the radio wave strength of the wireless access point 20 drops significantly while the wireless station 30 is in the TWT standby state in all frequency bands, it is necessary to search for a new wireless access point 20 again and attempt to connect to the wireless access point 20 after switching to the normal state. As a result, it becomes impossible to start communication immediately after switching to the normal state, and communication stability decreases. On the other hand, if all frequency bands are in the normal state, communication stability increases but power consumption increases.

[0043] Hereinafter, a first embodiment and a second embodiment for solving this type of problem will be described.

[0044] 2 shows a schedule generated by the schedule generation unit 32c of the first embodiment. The schedule generation unit 32c generates a schedule, for example, before starting wireless communication (schedule generation process, schedule generation step). The schedule generation unit 32c may generate a schedule based on information input by a user, for example, or may generate a schedule based on information received from another device such as the management device 10. Furthermore, the schedule generation unit 32c may generate a schedule after determining the wireless access point 20 to connect to.

[0045] The schedule elements shown in Figure 2 are the building blocks of a schedule, and a schedule is generated by repeatedly applying the schedule elements. Specifically, the horizontal axis of the schedule elements in Figure 2 represents time, meaning that after reaching the end (right end) of the schedule element, it returns to the beginning (left end) of the schedule element. In other words, a schedule is generated by repeatedly applying the schedule elements as a fixed time (finite time length) unit.

[0046] As shown in Fig. 2, the schedule elements describe, for each frequency, whether to enable a PS state and whether to enable a normal state or a TWT standby state. In the following description, canceling a valid state A and enabling another state B may be referred to as switching (from state A) to state B. In addition, for ease of understanding, the schedule elements in Fig. 2 do not take into account transition times or processing wait times.

[0047] The schedule elements in Fig. 2 are a schedule for achieving both communication stability (specifically, shortening the period during which communication is unavailable) and low power consumption. When the wireless station 30 performs communication that requires high throughput, the wireless station 30 performs communication in a state different from the schedule shown in Fig. 2, for example, by simultaneously using all frequency bands. In other words, the wireless station 30 is in a normal state in all frequency bands and in a state in which the PS state is canceled.

[0048] First, the PS schedule will be described. As shown in Figure 2, PS mode is first enabled in the 2.4 GHz band. Then, when PS mode is deactivated in the 2.4 GHz band, PS mode is enabled in the 5 GHz band. Considering the transition time and processing wait time described above, the timing when PS mode is deactivated in the 2.4 GHz band and the timing when PS mode is enabled in the 5 GHz band are likely not to strictly coincide. Therefore, the concept of a "time slot" is used to explain such events. A time slot refers to one of the time slots obtained by dividing the schedule into predetermined time periods. The length of a time slot cannot be uniquely determined because it varies depending on factors such as the wireless communication standard, processing speed, required time accuracy, and communication speed, but it is a length of time that is recognizable by those skilled in the art. Taking the above into consideration, the above point can be rephrased using the term "time slot": During the time slot when PS mode is deactivated in the 2.4 GHz band, PS mode is enabled in the 5 GHz band. Subsequently, during the time slot when PS mode is deactivated in the 5 GHz band, PS mode is enabled in the 6 GHz band.

[0049] The schedule elements in Figure 2 have the following characteristics regarding PS. That is, in each time period, at least one frequency band is in PS state, and the PS state is canceled in the other frequency bands. In PS state, the wireless communication function is enabled every time a return signal is received, so it is possible to detect the radio wave strength of the connected wireless access point 20. It is also possible to detect when the beacon of the wireless access point 20 can no longer be detected, in other words, when communication with the wireless access point 20 can no longer be performed.

[0050] Next, we will explain the TWT schedule. As shown in Figure 2, the 2.4 GHz band is first in normal mode, and the 5 GHz and 6 GHz bands are in TWT standby mode. Next, during the time period when the 2.4 GHz band switches to TWT standby mode, the 5 GHz band switches to normal mode. Next, during the time period when the 5 GHz band switches to TWT standby mode, the 6 GHz band switches to normal mode.

[0051] The schedule elements in Figure 2 have the following characteristics regarding TWT. That is, in each time period, one frequency band is always in normal mode, and the other frequency bands are in TWT standby mode. Note that the PS mode and normal mode are a set, and frequency bands in PS mode are scheduled to be in normal mode. In other words, frequency bands in which the PS mode is canceled are scheduled to be in TWT standby mode.

[0052] As a result, when in PS state and normal state, the wireless communication function is enabled every time a recovery signal is received, making it possible to detect the radio wave strength of the connected wireless access point 20. On the other hand, when in TWT standby state, no signals, including recovery signals, are accepted, but power consumption is low. In other words, by setting one of the three frequency bands to PS state and normal state, power consumption can be minimized while detecting the radio wave strength of the wireless access point 20. At this time, the other two frequency bands are in TWT standby state, so almost no power is consumed. Therefore, the total power consumption of the three frequency bands can also be reduced. On the other hand, one frequency band is in PS state and normal state throughout all time periods, so the radio wave strength of the wireless access point 20 can be detected throughout all time periods. As a result, it is possible to achieve both stable communication and low power consumption.

[0053] Furthermore, the communication adjustment unit 32d of the wireless station 30 uses a power saving function that reduces at least one of the number of streams and the bandwidth for the frequency band in the PS state, turning off the circuitry around the antenna used for communication and reducing the power required for communication. Since the purpose of the PS state is to detect the radio wave strength of the wireless access point 20, a high communication speed is not required. Therefore, there is no problem even if the number of streams and the bandwidth are reduced, and the only effect achieved is reduced power consumption.

[0054] Fig. 3 shows a sequence diagram for starting wireless communication according to the schedule in Fig. 2. Below, the flow of each process will be explained according to this sequence diagram.

[0055] After starting up, the wireless station 30 performs an MLO connection process with the wireless access point 20. The MLO connection process is a setting for performing communication using multiple (three in this case) frequency bands simultaneously. Next, when the wireless station 30 determines that high throughput is not required, it performs a TWT start process for the 6 GHz band to switch the 6 GHz band to a TWT standby state, performs a TWT start process for the 5 GHz band to switch the 5 GHz band to a TWT standby state, and performs a PS start process for the 2.4 GHz band to switch the 2.4 GHz band to a PS state. In this state, the radio wave strength of the wireless access point 20 is detected using the 2.4 GHz band, and the control unit 32 determines whether the radio wave strength is equal to or less than a threshold.

[0056] After that, the radio station 30 performs TWT termination processing for the 5 GHz band to switch the 5 GHz band to the normal state, and performs PS initiation processing for the 5 GHz band to switch the 5 GHz band to the PS state. Furthermore, the radio station 30 performs PS termination processing for the 2.4 GHz band to cancel the PS state in the 2.4 GHz band, and performs TWT initiation processing for the 2.4 GHz band to switch the 2.4 GHz band to the TWT standby state. Because the processing is performed sequentially, strictly speaking, there is a timing when the PS state is enabled for both the 2.4 GHz and 5 GHz bands. However, in the timing chart of FIG. 2, the PS state is enabled for only one frequency band in each time period, and in the sequence diagram of FIG. 3, switching to the 5 GHz PS state and canceling the 2.4 GHz PS state are performed in a single processing sequence, so this corresponds to "one frequency band being set to the PS state."

[0057] In this state, the radio wave strength of the wireless access point 20 (wireless access point A in FIG. 3) is detected using the 5 GHz band, and the control unit 32 constantly determines whether the radio wave strength is equal to or less than a threshold. If the control unit 32 determines that the radio wave strength is equal to or less than the threshold, it performs MLO roaming processing. The MLO roaming processing is a process of switching the destination wireless access point 20 (from wireless access point A to wireless access point B in FIG. 3) and performing the above-mentioned MLO connection processing. That is, in the first embodiment, when the radio wave strength in one of the three frequency bands becomes equal to or less than a threshold, the wireless station 30 performs MLO roaming processing regardless of the radio wave strength in the other frequency bands.

[0058] This reduces power consumption while quickly detecting a decrease in the radio wave intensity of the currently connected wireless access point 20 (including when the connection with the wireless access point 20 is cut off), and allows the device to reconnect to a new wireless access point 20.

[0059] Next, a second embodiment will be described. In the following description, the same or similar matters as those in the first embodiment may be omitted.

[0060] FIG. 4 shows schedule elements of the second embodiment. In the schedule elements of the first embodiment, each state is uniformly allocated to the three frequency bands. In contrast, in the second embodiment, scheduling is performed so that the length of time that the 6 GHz band is in the PS state (and normal state, the same applies below) is increased. Specifically, in the first embodiment, the PS state is enabled in the order of the 2.4 GHz band, the 5 GHz band, and the 6 GHz band, and the length of time that the PS state is in each frequency band is also the same. In contrast, in the second embodiment, the length of time that the PS state is in the two frequency bands (2.4 GHz and 6 GHz, or 5 GHz and 6 GHz) is different. Specifically, the PS state is enabled in the order of the 2.4 GHz band, the 6 GHz band, the 5 GHz band, and the 6 GHz band, so that the 6 GHz band is frequently in the PS state. Furthermore, the length of time that the PS state is in each instance is longer in the 6 GHz band than in the other frequency bands. As a result, in the second embodiment, the total length of time during which the device is in PS state in the 6 GHz band is longer than the total length of time during which the device is in normal state in the 2.4 GHz band, and is also longer than the total length of time during which the device is in normal state in the 5 GHz band.

[0061] As described above, in the second embodiment, the radio wave intensity of the connected wireless access point 20 is detected primarily using the 6 GHz band. Here, because the 6 GHz band is a higher frequency band than the other frequency bands, the communication distance in the 6 GHz band is shorter than in the other frequency bands. Therefore, if proper communication with the wireless access point 20 is possible in the 6 GHz band, it is highly likely that proper communication will also be possible in the other two frequency bands. Therefore, by determining the radio wave intensity of the wireless access point 20 primarily using communication in the 6 GHz band, it becomes easier to maintain a state in which communication is possible using all frequency bands simultaneously. Furthermore, when the communication unit 31 communicates using two frequency bands, for example, the 2.4 GHz band and the 5 GHz band, it is preferable to determine the radio wave intensity of the wireless access point 20 by using communication in the 5 GHz band, which is the higher frequency band, for a longer period of time than by using communication in the other frequency band, the 2.4 GHz band. This makes it easier to maintain a state in which communication is possible using both frequency bands simultaneously. Furthermore, even when communication is performed using a combination of frequency bands other than these, the same effect can be achieved by setting the same conditions, i.e., the condition that the highest frequency band among multiple frequency bands is used for a longer period of time than the other frequency bands to detect radio wave intensity.

[0062] Fig. 5 shows a sequence diagram for starting wireless communication according to the schedule of the second embodiment shown in Fig. 4. Below, the flow of each process will be explained according to this sequence diagram.

[0063] After starting up, the wireless station 30 performs an MLO connection process with the wireless access point 20. Next, as in the first embodiment, if the wireless station 30 determines that high throughput is not required, it performs a TWT start process for the 6 GHz band to switch the 6 GHz band to a TWT standby state, performs a TWT start process for the 5 GHz band to switch the 5 GHz band to a TWT standby state, and performs a PS start process for the 2.4 GHz band to switch the 2.4 GHz band to a PS state. In this state, the radio wave strength of the wireless access point 20 is detected using the 2.4 GHz band, and the control unit 32 determines whether the radio wave strength is equal to or less than a threshold.

[0064] After that, the wireless station 30 performs TWT termination processing for the 6 GHz band to switch the 6 GHz band to the normal state, and performs PS initiation processing for the 6 GHz band to switch the 6 GHz band to the PS state. Furthermore, the wireless station 30 performs PS termination processing for the 2.4 GHz band to cancel the PS state for the 2.4 GHz band, and performs TWT initiation processing for the 2.4 GHz band to switch the 2.4 GHz band to the TWT standby state. In this state, the radio wave intensity of the wireless access point 20 is detected using the 6 GHz band.

[0065] FIG. 5 also shows that the time length for detecting the radio wave strength of the wireless access point 20 using the 6 GHz band is longer than when using other frequency bands. After that, the wireless station 30 performs TWT termination processing for the 5 GHz band to switch the 5 GHz band to the normal state, and performs PS initiation processing for the 5 GHz band to switch the 5 GHz band to the PS state. Furthermore, the wireless station 30 performs PS termination processing for the 6 GHz band to cancel the PS state for the 6 GHz band, and performs TWT initiation processing for the 6 GHz band to switch the 6 GHz band to the TWT standby state. In this state, the radio wave strength of the wireless access point 20 is detected using the 5 GHz band. Thereafter, the states are switched based on the schedule elements in FIG. 4.

[0066] As described above, the wireless communication station connects to the wireless access point 20 and performs wireless communication. The wireless communication station of this embodiment includes a communication unit 31 and a control unit 32. The communication unit 31 communicates using multiple frequency bands simultaneously. The control unit 32 controls the communication unit 31. The control unit 32 includes a PS execution unit 32a, a TWT execution unit 32b, and a schedule generation unit 32c. The PS execution unit 32a uses PS to switch, for each frequency band, between a PS state in which the wireless communication function is put to sleep and a PS state in which the wireless communication function is restored from sleep every time a recovery signal is received from the wireless access point 20. The TWT execution unit 32b uses TWT to switch, for each frequency band, between a normal state in which the wireless communication function is enabled and a TWT standby state in which the wireless communication function is disabled and signals including a recovery signal are not accepted (state switching process, state switching step). The schedule generation unit 32c generates a schedule that determines, for each frequency band, whether to enable the PS state and whether to enable the normal state or the TWT standby state (schedule generation process, schedule generation step). In the schedule generated by the schedule generating unit 32c, at least one frequency band is set to be in the normal state in each time period, and to be in the PS state at least temporarily during the normal state.

[0067] As a result, at least one frequency band is in a normal state during each time period, and it is possible to detect early on that the radio wave strength of the wireless access point 20 has weakened. As a result, it is possible to quickly reconnect to a more appropriate wireless access point 20, ensuring communication stability (more specifically, shortening the period during which communication is unavailable). Furthermore, although there is a trade-off between communication stability and power consumption, power consumption can be reduced by setting the device to be in the PS state at least temporarily during the normal state.

[0068] In the wireless communication station of this embodiment, the schedule generation unit 32c repeatedly applies a single generated schedule element of finite time length, and the total length of time during which the schedule element is in the normal state differs between at least two frequency bands.

[0069] This allows the length of time during which the normal state is maintained to vary depending on the characteristics of the frequency band, making it possible to create a wireless communication environment that meets the needs of the user.

[0070] In the wireless communication station of this embodiment, in a schedule element, the total length of time during which the highest frequency band among multiple frequency bands is in a normal state is longer than the total length of time during which any one frequency band other than the highest frequency band is in a normal state.

[0071] This allows the connection status with wireless access point 20 to be determined mainly using communication in the highest frequency band (in other words, the frequency band with the shortest communication distance), making it easier to maintain a state in which communication is possible using all frequency bands simultaneously.

[0072] In the wireless communication station of this embodiment, the communication unit 31 has a function of communicating simultaneously using the 2.4 GHz band, the 5 GHz band, and the 6 GHz band. In the schedule elements, the total length of time during which the 6 GHz band is in the normal state is longer than the total length of time during which the 2.4 GHz band is in the normal state and is also longer than the total length of time during which the 5 GHz band is in the normal state.

[0073] Since the communication distance in the 6 GHz band is shorter than the communication distance in the other two frequency bands, if proper communication with wireless access point 20 is possible in the 6 GHz band, it is highly likely that proper communication will also be possible in the other two frequency bands. Therefore, by determining the connection status with wireless access point 20 mainly using communication in the 6 GHz band, it becomes easier to maintain a state in which communication is possible using all frequency bands simultaneously.

[0074] In the wireless communication station of this embodiment, the schedule generated by the schedule generating unit 32c is set so that at least one frequency band is in the PS state in each time period.

[0075] This allows the PS state to be used effectively, further reducing power consumption.

[0076] In the wireless communication station of this embodiment, the communication unit 31 has a function of communicating simultaneously using three frequency bands. In the schedule generated by the schedule generation unit 32c, two frequency bands are set to be in a TWT standby state and the remaining frequency band is set to be in a PS state in each time period.

[0077] This allows the TWT standby state and PS state to be used effectively, further reducing power consumption.

[0078] In the wireless communication station of this embodiment, the control unit 32 includes a communication adjustment unit 32d that reduces power related to communication by reducing at least one of the number of streams and the bandwidth used for communication with the wireless access point 20. The communication adjustment unit 32d reduces power related to communication for a frequency band that is in the PS state.

[0079] This allows power consumption to be further reduced.

[0080] In the wireless communication station of this embodiment, when the control unit 32 determines that the radio wave strength of the wireless access point 20 in one of the multiple frequency bands in which the communication unit 31 can communicate has fallen below a threshold, the control unit 32 controls the communication unit 31 to connect to a new wireless access point 20, regardless of the radio wave strength of the wireless access point 20 in other frequency bands.

[0081] This makes it easier to maintain a state in which communication using multiple frequency bands can be carried out simultaneously.

[0082] The preferred embodiment of the present invention has been described above, but the above configuration can be modified, for example, as follows. Each modification may be made alone, or multiple modifications may be made in any combination.

[0083] The management device 10 is not an essential component, and depending on the purpose of the wireless communication system 1, the management device 10 can be omitted.

[0084] The wireless station 30 is not limited to being mounted on the cart 40, but may be mounted on another mobile body. The wireless station 30 may also be installed on a device other than a mobile body. Even in this case, the present invention can be effectively utilized when the wireless communication environment changes due to the presence of a moving radio wave shielding object along the communication path or the movement of the wireless access point 20.

[0085] The sequence diagrams shown in the above embodiments are merely examples, and some processes may be omitted, some processes may be changed, or new processes may be added. For example, the timing of switching states may be switched sequentially for each frequency band, or the states of multiple frequencies may be switched simultaneously or in parallel. Furthermore, the order of switching states is merely an example, and is not limited to the order disclosed in the above embodiments.

[0086] In the above embodiment, when the radio wave strength of a wireless access point 20 in any one frequency band falls below a threshold, a connection is made to a new wireless access point 20. Alternatively, when the radio wave strength of a wireless access point 20 in multiple (e.g., two) frequency bands falls below a threshold, a connection may be made to a new wireless access point 20. In this case, it is preferable to immediately check the radio wave strength of the wireless access point 20 in one frequency band after the radio wave strength of the wireless access point 20 in the other frequency bands falls below a threshold.

[0087] The schedules shown in the first and second embodiments are merely examples, and other schedules may be used. For example, if it is desired to reduce the frequency of roaming in communication using three frequency bands, the duration of the normal state of, for example, 5 GHz (or 2.4 GHz instead) may be made longer than the durations of the other two frequency bands.

[0088] In the first and second embodiments, the frequency bands are scheduled to always be in the PS state during the normal state. Alternatively, the frequency bands may be scheduled to be in the PS state only for part of the normal state. Furthermore, in the first and second embodiments, the frequency bands are scheduled to always be in the PS state during each time period. Alternatively, there may be no frequency band in the PS state during each time period, or multiple frequency bands may be in the PS state simultaneously. [Explanation of symbols]

[0089] 1. Wireless communication systems 20 Wireless Access Points 30 Radio Stations 31 Communications Department 32 Control Unit 32a PS Executive Department 32b TWT Executive Department 32c Schedule Generation Unit 32d Communications Coordination Department

Claims

1. In a wireless communication station that connects to a wireless access point and performs wireless communication, a communication unit that communicates using multiple frequency bands simultaneously; a control unit that controls the communication unit; Equipped with The control unit a PS execution unit that uses PS (Power Save) to put a wireless communication function into a sleep state for each frequency band and switches the state to a PS state in which the wireless communication function is restored from the sleep state every time a restoration signal is received from the wireless access point; a TWT execution unit that switches, for each frequency band, between a normal state in which a wireless communication function is enabled and a TWT standby state in which the wireless communication function is disabled and signals including the recovery signal are not accepted by using a TWT (Target Wake Time); a schedule generating unit that generates a schedule that determines whether to enable the PS state and whether to enable the normal state or the TWT standby state for each of the frequency bands; Equipped with A wireless communication station characterized in that, in the schedule generated by the schedule generation unit, at least one of the frequency bands is set to be in the normal state during each time period and to be in the PS state at least temporarily during the normal state.

2. 2. A wireless communication station according to claim 1, the schedule generation unit repeatedly applies the generated schedule element of a finite time length; A wireless communication station, characterized in that the total length of time during which the normal state is maintained in the schedule elements differs between at least two of the frequency bands.

3. 3. A wireless communication station according to claim 2, A wireless communication station characterized in that, in the schedule element, the total length of time during which the normal state is in the highest frequency band among the plurality of frequency bands is longer than the total length of time during which the normal state is in any one of the frequency bands other than the highest frequency band.

4. 3. A wireless communication station according to claim 2, the communication unit has a function of communicating simultaneously using the 2.4 GHz band, the 5 GHz band, and the 6 GHz band, A wireless communication station characterized in that, in the schedule element, the total length of time during which the normal state is in place in the 6 GHz band is longer than the total length of time during which the normal state is in place in the 2.4 GHz band, and is also longer than the total length of time during which the normal state is in place in the 5 GHz band.

5. 2. A wireless communication station according to claim 1, The wireless communication station is characterized in that, in the schedule generated by the schedule generating unit, at least one of the frequency bands is set to be in the PS state in each time period.

6. 2. A wireless communication station according to claim 1, the communication unit has a function of communicating using the three frequency bands simultaneously, A wireless communication station characterized in that, in the schedule generated by the schedule generation unit, two of the frequency bands are set to be in the TWT standby state and the remaining one of the frequency bands is set to be in the PS state during each time period.

7. 2. A wireless communication station according to claim 1, the control unit includes a communication adjustment unit that reduces at least one of the number of streams and the bandwidth used in communication with the wireless access point to reduce power related to communication, The wireless communication station is characterized in that the communication adjustment unit reduces power related to communication for the frequency band in the PS state.

8. 2. A wireless communication station according to claim 1, A wireless communication station characterized in that, when the control unit determines that the radio wave strength of the wireless access point in one of the multiple frequency bands in which the communication unit can communicate has fallen below a threshold, the control unit controls the communication unit to connect to a new wireless access point, regardless of the radio wave strength of the wireless access point in the other frequency bands.

9. A wireless communication method using a wireless communication station that connects to a wireless access point and performs wireless communication, the wireless communication station is capable of communicating using a plurality of frequency bands simultaneously; the wireless communication station is capable of switching to a PS state in which a wireless communication function is put to sleep for each of the frequency bands by using a PS (Power Save) and is restored from sleep every time a restoration signal is received from the wireless access point; the wireless communication station is capable of switching between a normal state in which a wireless communication function is enabled and a TWT standby state in which the wireless communication function is disabled and the wireless communication station does not accept signals including the return signal by using a TWT (Target Wake Time); a schedule generating step of generating a schedule that determines whether the PS state is enabled and whether the normal state or the TWT standby state is enabled for each of the frequency bands; a state switching step of switching whether to enable the PS state and whether to enable the normal state or the TWT standby state for each frequency band based on the schedule generated in the schedule generating step; A wireless communication method comprising:

10. A wireless communication program for causing a wireless communication station to connect to a wireless access point and perform wireless communication, the wireless communication station is capable of communicating using a plurality of frequency bands simultaneously; the wireless communication station is capable of switching to a PS state in which a wireless communication function is put to sleep for each of the frequency bands by using a PS (Power Save) and is restored from sleep every time a restoration signal is received from the wireless access point; the wireless communication station is capable of switching between a normal state in which a wireless communication function is enabled and a TWT standby state in which the wireless communication function is disabled and the wireless communication station does not accept signals including the return signal by using a TWT (Target Wake Time); a schedule generating step of generating a schedule that determines whether the PS state is enabled and whether the normal state or the TWT standby state is enabled for each of the frequency bands; a state switching step of determining whether to enable the PS state and switching whether to enable the normal state or the TWT standby state for each frequency band based on the schedule generated in the schedule generating step; a wireless communication station for receiving a wireless signal from said wireless communication station;

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