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

Abstract

To perform appropriate communication control depending on a change in radio environment.SOLUTION: A radio device 10 comprises: an acquisition unit 131 for acquiring a time used for transmission of data to a second communication device 22 in a first period including the current time as its end and a time used by the radio device 10 for transmission of a management frame; an estimation unit 132 that uses the time used for transmission of the data, the time used for transmission of the management frame, and a time to be used for transmission of the management frame in a second period including the current time as its start to estimate a time available for transmission of new data to the second communication device 22 in the second period so that the total sum of radio transmission times in the first period and the second period does not exceed a predetermined time ratio with respect to the total sum of the first period and the second period; and a calculation unit 133 for calculating a communication band available for transmission of the new data to the second communication device 22 by multiplying the time available for transmission of the new data by a data rate.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] IEEE standard 802.11ah (hereinafter referred to as 802.11ah) is a wireless communication method that uses the 920 MHz frequency band and is expected to be used in a variety of fields, especially as a communication system for the Internet of Things (IoT). For example, 802.11ah does not require a proprietary protocol or dedicated system, and is highly compatible with existing IP (Internet Protocol) assets and commercially available IP-based devices, allowing for the effective use of existing IP assets. Furthermore, 802.11ah is a standard that uses unlicensed bands, allowing for the flexible installation of base stations and terminals according to the usage scenario.

[0003] However, in the frequency band used by 802.11ah (for example, the 920 MHz band), the Radio Law restricts radio wave transmission to a maximum of 360 seconds per hour. To comply with this restriction, for example, Patent Document 1 discloses a wireless communication system that limits the total transmission time per unit time from the transmission of radio waves to a first time limit or less, permits wireless transmission at a transmission timing for each predetermined transmission cycle, and controls transmission so that the wireless transmission time per transmission is less than a second time limit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-104026 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the technology described in Patent Document 1, for example, while it is possible to comply with the transmission time limit per unit time after transmitting radio waves due to the limitations imposed by the first and second time limits, there are cases where it is not possible to perform appropriate communication control in response to the ever-changing wireless environment. Also, if it is in accordance with the rule that radio waves must not be transmitted when the upper limit of the transmission time limit per unit time is reached, communication will suddenly be interrupted at the time the upper limit of the transmission time limit is reached, and data that should be transmitted will only be retransmitted after an appropriate amount of time has passed, which may prevent appropriate communication control, or in other words, may reduce communication efficiency.

[0006] The present invention has been made to solve the above problems, and has an object to provide a wireless device or the like that can perform appropriate communication control in response to changes in the wireless environment. [Means for solving the problem]

[0007] In order to solve the above problem, a wireless device according to one aspect of the present invention is a wireless device that transmits data acquired from a first communication device to a second communication device using a predetermined communication standard, wherein the predetermined communication standard limits the wireless transmission available time per unit time to a predetermined time ratio or less, and the wireless device includes an acquisition unit that acquires the time used by the wireless device to transmit the data to the second communication device and the time used by the wireless device to transmit a management frame during a first period ending at the current time, and an acquisition unit that acquires the time used to transmit the data, the time used to transmit the management frame, and the time used to transmit the management frame during a second period starting at the current time. an estimation unit that estimates a time available for the wireless device to transmit new data to the second communication device during the second period, using the time used to transmit a frame, such that the sum of the wireless transmission time during the first period and the wireless transmission time during the second period does not exceed the predetermined time ratio with respect to the total time of the first period and the second period; and a calculation unit that calculates a communication bandwidth that the wireless device can use to transmit the new data to the second communication device during the second period by multiplying the time available for transmitting the new data by a data rate that is a communication speed between the wireless device and the second communication device.

[0008] According to this, when a wireless device acquires new data from a first communication device, the wireless device can estimate the time available for transmitting new data to the second communication device in the next fixed time period from the time used to transmit data to the second communication device during a first period ending at the current time (in other words, the most recent transmission record). Furthermore, the wireless device can calculate the communication bandwidth available for transmitting new data to the second communication device by multiplying the estimated time by the data rate at the current time. Therefore, even if the data rate fluctuates depending on the state of wireless communication, the wireless device can calculate the communication bandwidth available for transmitting new data to the second communication device in accordance with the fluctuation in the data rate. Therefore, the wireless device can perform appropriate communication control in accordance with changes in the wireless environment.

[0009] The wireless device may further include a bandwidth limiting unit that limits the communication speed of data that the wireless device acquires from the first communication device during the second period, in accordance with the communication bandwidth calculated by the calculation unit.

[0010] According to this, the wireless device can limit the communication speed of new data acquired from the first communication device during the second time period starting from the current time, in accordance with the communication bandwidth calculated by the calculation unit, and therefore can limit the amount of new data acquired from the first communication device to the amount that can be transmitted to the second communication device within the available transmission time.

[0011] In addition, the wireless device may further include a bandwidth limiting unit that transmits control information to the first communication device including an instruction to limit the communication speed of the new data that the first communication device transmits to the wireless device during the second period, in accordance with the communication bandwidth calculated by the calculation unit.

[0012] According to this, the wireless device can limit the communication speed of new data transmitted from the first communication device to the wireless device during the second time period starting from the current time, in accordance with the communication bandwidth calculated by the calculation unit, and thus can limit the amount of new data transmitted from the first communication device to the amount that can be transmitted within the time available for transmission to the second communication device.

[0013] The first period and the second period may have the same time length.

[0014] This allows the wireless device to control communications using a control cycle of the same length of time, making it easier to perform appropriate communication control in response to changes in the wireless environment.

[0015] The wireless device may include the first communication device.

[0016] This makes it easier for the wireless device to adjust the amount of data acquired from the first communication device because the wireless device is less susceptible to the communication environment.

[0017] The predetermined communication standard may be IEEE802.11ah.

[0018] This allows the wireless device to perform appropriate communication control in response to changes in the wireless environment even under IEEE802.11ah.

[0019] Furthermore, a communication system according to one aspect of the present invention comprises the above-described wireless device and the first communication device, wherein the first communication device performs a compression process on moving image data and transmits the compressed moving image data as the data, and the wireless device sets a compression rate for the compression process of the first communication device during the second period in accordance with the communication bandwidth calculated by the calculation unit, and transmits the set compression rate to the first communication device.

[0020] This allows the communication system to transmit moving image data compressed at an appropriate compression rate in response to changes in the wireless environment.

[0021] Furthermore, a control method for a wireless device according to one aspect of the present invention is a control method for a wireless device that transmits data acquired from a first communication device to a second communication device using a predetermined communication standard, wherein the predetermined communication standard limits the wireless transmission available time per unit time to a predetermined time ratio or less, and the wireless device includes an acquisition step of acquiring the time used by the wireless device to transmit the data to the second communication device and the time used by the wireless device to transmit a management frame during a first period ending at the current time; and an acquisition step of acquiring the time used to transmit the data, the time used to transmit the management frame, and the time used to transmit the management frame during a second period starting at the current time. and a calculation step of calculating a communication bandwidth available for the wireless device to transmit the new data to the second communication device in the second period by multiplying the time available for transmitting the new data by a data rate that is a communication speed between the wireless device and the second communication device.

[0022] This provides the same effects as the wireless device described above.

[0023] A program according to one aspect of the present invention is a program that causes one or more computers to execute the above-described method for controlling a wireless device.

[0024] This provides the same effects as the wireless device described above.

[0025] The present invention can be realized not only as an apparatus, but also as a method in which the processing means constituting the apparatus are steps, as a program that causes a computer to execute those steps, as a computer-readable recording medium such as a CD-ROM on which the program is recorded, or as information, data, or signals that represent the program.These programs, information, data, and signals may be distributed via a communication network such as the Internet. [Effects of the Invention]

[0026] According to the present invention, a wireless device can perform appropriate communication control in response to changes in the wireless environment. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is an explanatory diagram showing the operation of a conventional wireless device. [Figure 2] FIG. 2 is a graph showing the transition of the time used by a wireless device for management frames. [Figure 3] FIG. 3 is a graph showing the transition of the remaining time when a communication load is applied to the wireless device in the situation shown in FIG. [Figure 4] FIG. 4 is a schematic diagram illustrating an example of the configuration of a communication system including a wireless device according to an embodiment. [Figure 5] FIG. 5 is a flowchart illustrating an example of processing executed by the wireless device according to the embodiment. [Figure 6] FIG. 6 is a schematic diagram for explaining an example of the operation of the band limiting unit in the band limiting step. [Figure 7] FIG. 7 is a first diagram specifically illustrating the estimation process executed by the wireless device according to the embodiment. [Figure 8] FIG. 8 is a second diagram specifically illustrating the estimation process executed by the wireless device according to the embodiment. [Figure 9]FIG. 9 is a third diagram specifically illustrating the estimation process executed by the wireless device according to the embodiment. [Figure 10] FIG. 10 is a fourth diagram specifically illustrating the estimation process executed by the wireless device according to the embodiment. [Figure 11] FIG. 11 is a schematic diagram for explaining another example of the operation of the band limiting unit in the band limiting step. [Figure 12] FIG. 12 is a schematic diagram for explaining an example of the operation of the band limiting unit when the wireless device includes the first communication device. [Figure 13] FIG. 13 is a schematic diagram illustrating an example of the configuration of a video distribution system including a wireless device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0028] (Findings that led to the present invention) First, a conventional wireless device and its problems will be described. Fig. 1 is an explanatory diagram showing the operation of a conventional wireless device.

[0029] As explained in the Background section, in Japan, there is a rule that 802.11ah, which uses the 920 MHz band, can only transmit radio waves for 360 seconds per hour (i.e., the transmittable time ratio = 10%). In other words, there is a rule that 802.11ah can only transmit radio waves for 10% of the time, meaning that the time ratio during which radio waves can be transmitted is 10% of the time. The time ratio is also called the predetermined time ratio.

[0030] Conventional wireless devices comply with the above rules by controlling communications so as not to violate the above rules (more specifically, so that radio wave transmission does not exceed 360 seconds per hour) by limiting the total transmission time per unit time from the start of radio wave transmission to a time limit or less.

[0031] For example, as shown in Figure 1, when a conventional wireless device transmits data acquired from a first communication device to a second communication device, if there is data (also called a communication packet) that would cause the wireless transmission time per transmission to exceed the time limit, the conventional wireless device adjusts the amount of data to be transmitted to the second communication device by discarding the data (communication packet) before transmission.

[0032] In this way, conventional wireless devices control wireless communication with a second communication device, but discard data that would be transmitted beyond the time limit, which may degrade the quality of applications or services that use communication (for example, dropping frames in an application that transmits video data, or skipping audio, etc.).

[0033] In order to avoid the above-mentioned degradation in quality, there is a method of adjusting the data transmission rate to the second communication device without discarding the data obtained from the first communication device as described above, but this method is considered difficult to implement for reasons (1) or (2) below.

[0034] (1) The communication bandwidth that the wireless device can use to communicate with the second communication device varies in conjunction with the data rate, which is the signal transmission speed in communication between the wireless device and the second communication device and varies depending on the wireless environment.

[0035] (2) This is because the time used by the wireless device for management frames cannot be subject to bandwidth restrictions. Note that wireless devices generally transmit management frames to the second communication device at the slowest data rate. The management frames referred to here are management frames in wireless communication that are used for communications necessary to maintain wireless communication.

[0036] An example of the time used by a wireless device for a management frame will be described with reference to FIG.

[0037] 2 is a graph showing the transition of the time used by a wireless device for management frames. Here, the unit time (also called the management unit time) managed as the time interval used to calculate the transmission time is set to be shorter than one hour (i.e., 3600 seconds), for example, one minute (i.e., 60 seconds). That is, in this example, communication control is performed so that the transmission time is limited to 6 seconds for one minute (i.e., 60 seconds) as the management unit time, while leaving the predetermined time ratio of 10% unchanged, rather than limiting the transmission time to 360 seconds for one hour (i.e., 3600 seconds) as the management unit time.

[0038] 2, the horizontal axis of the graph indicates time, with the time when the wireless device is powered on being time 0. The vertical axis of the graph indicates the time (also referred to as remaining time) that the wireless device can use to communicate with the second communication device within a 6-second period starting from the current time.

[0039] In Figure 2, the remaining time is shown every two seconds. The remaining time is calculated by subtracting the time spent by the wireless device to transmit frames (also called the consumed time) during the 60-second period ending at that point in time every two seconds from the 6-second time limit.

[0040] When a wireless device is powered on, it starts transmitting management frames, and repeats the transmission of management frames at a predetermined interval. As a result, the remaining time shown in FIG. 2 decreases over time. A management frame is, for example, a beacon frame. A wireless device transmits a beacon frame once every 100 milliseconds. In this case, if the time it takes to transmit one beacon frame is 3.3 milliseconds, then the transmission time consumed in the 60-second management unit time is 600 times x 3.3 milliseconds, or approximately 2 seconds.

[0041] Once 60 seconds have passed since the power was turned on, the time used to send management frames for more than 60 seconds prior to that point is no longer included in the consumed time (in other words, that consumed time is no longer counted as past transmission results). Therefore, the remaining time after 60 seconds has passed is maintained at approximately 4 seconds, balancing the decrease in the time used to send management frames for more than 60 seconds prior to that point with the increase in the time used to send new management frames.

[0042] Here, since management frames are always transmitted at the slowest data rate, the time used for management frames remains constant. Note that in FIG. 2, beacon frames are used as management frames in wireless communication as an example, but this is not limiting. In other words, any communication that is necessary to maintain wireless communication and that is performed at a predetermined interval for a predetermined period of time may be used. Specifically, this includes communication that is performed when updating DHCP (Dynamic Host Configuration Protocol).

[0043] In such a situation, if the wireless device transmits data in addition to transmitting a management frame, the situation shown in Fig. 3 may occur. Fig. 3 is a graph showing the transition of the remaining time when the wireless device transmits data and a communication load is imposed in the situation shown in Fig. 2. Here, an example is shown in which the wireless device starts to obtain data from the first communication device 30 seconds after the wireless device is turned on, and transfers the obtained data to the second communication device.

[0044] As shown in Figure 3, for 30 seconds after the wireless device is turned on, the wireless device only transmits management frames and does not transmit data, just as in Figure 2. Therefore, for 30 seconds after the wireless device is turned on, the remaining time decreases. This is because the time used to transmit management frames increases as time passes, and the time used to transmit management frames is deducted from the 6-second time limit as consumed time.

[0045] Next, from the time the wireless device starts receiving data from the first communication device and transmitting the data to the second communication device (30 seconds elapsed) until 60 seconds later, the rate at which the remaining time decreases increases. This is because, as time passes, both the time used to transmit the management frame and the time used to transmit data to the second communication device increase, and both of these times are deducted as consumed time from the 6-second time limit.

[0046] Next, when the time elapsed since the power was turned on exceeds 60 seconds, the time used to transmit management frames for the past 60 seconds or more is no longer included in the consumed time (in other words, the consumed time is no longer counted as past transmission results). Therefore, the rate at which the remaining time decreases after 60 seconds has elapsed decreases accordingly. However, if the wireless device continues to transmit data to the second communication device, the remaining time will eventually reach 0 seconds, and the wireless device will no longer be able to communicate with the second communication device.

[0047] To avoid such a situation where communication becomes impossible, conventional wireless devices check past transmission records when transmitting data acquired from a first communication device to a second communication device, and if they determine that transmitting the data to the second communication device would result in a transmission time per hour exceeding a predetermined time ratio of 10%, they discard the data as mentioned at the beginning (see Figure 1).

[0048] However, as described above, discarding part of the data acquired by the wireless device may, for example, degrade the quality of applications or services that use communication with the second communication device (for example, it may cause frame drops in an application that transmits video data, or audio skipping, etc.).

[0049] Therefore, after extensive research, the inventors of the present application have found that by setting a management unit time shorter than the one hour specified by law and estimating the time available for the wireless device to transmit new data to the second communication device in the next management unit time so as not to exceed the time limit (a predetermined time ratio) based on the wireless device's transmission record in the most recent management unit time, it is possible to limit the amount of data that the wireless device acquires from the first communication device in accordance with the communication bandwidth available for transmitting new data to the second communication device. This makes it possible to provide a wireless device that can perform appropriate communication control in response to changes in the wireless environment.

[0050] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0051] The embodiments described below each illustrate a preferred specific example of the present invention. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept of the present invention will be described as optional components that constitute a more preferred embodiment. Note that identical components will be assigned the same reference numerals, and descriptions thereof may be omitted.

[0052] (Embodiment) In this embodiment, a communication system and a wireless device that can perform appropriate communication control in response to changes in the wireless environment will be described.

[0053] [1. Configuration] First, a configuration of a communication system including a wireless device according to the present embodiment will be described. Fig. 4 is a schematic diagram showing an example of the configuration of a communication system including a wireless device according to the present embodiment.

[0054] In this embodiment, the communication system 1 includes, for example, a wireless device 10, a first communication device 21, and a second communication device 22. In Fig. 4, the communication system 1 includes one first communication device 21 and one second communication device 22, but may include two or more.

[0055] The wireless device 10 transmits data acquired from the first communication device 21 to the second communication device 22 using a predetermined communication standard. The predetermined communication standard limits the wireless transmission time per unit time. For example, the predetermined communication standard is IEEE802.11ah. According to the above-mentioned rule, the wireless device 10 needs to control communication so that the wireless transmission time using 802.11ah does not exceed 360 seconds per hour (i.e., 3600 seconds).

[0056] In this embodiment, wireless device 10 acquires the time used for transmitting data to second communication device 22 from the transmission record with second communication device 22 during a first period that has the above-mentioned management unit time width (e.g., 60 seconds) and ends at the current time, estimates the time available for transmitting new data to second communication device 22 during a second period that has the above-mentioned management unit time width and starts at the current time, and multiplies the estimated time by the data rate to calculate the communication bandwidth available for transmitting new data to second communication device 22. However, the lengths of the first period and the second period do not need to be the same.

[0057] Furthermore, wireless device 10, in accordance with the calculated communication bandwidth, (i) limits the communication speed of new data acquired from first communication device 21 during the second period starting from the current time, or (ii) limits the communication speed of new data transmitted from first communication device 21 to wireless device 10 during the second period starting from the current time. This contributes to preventing data from accumulating in wireless device 10 (in other words, preventing wireless device 10 from continuing to hold received data without being able to transmit it).

[0058] The wireless device 10 includes, for example, a first communication unit 11, a second communication unit 12, a control unit 13, and a storage unit 14.

[0059] The first communication unit 11 is a communication circuit (or a communication module) that communicates with the first communication device 21. The first communication unit 11 may include, for example, at least one of a communication circuit for communicating via a wide area communication network and a communication circuit for communicating via a local communication network. Furthermore, the first communication unit 11 may be a wired communication circuit for performing wired communication, or a wireless communication circuit for performing wireless communication. The communication standard of the first communication unit 11 is not particularly limited.

[0060] The second communication unit 12 is a communication circuit (or a communication module) that performs wireless communication with the second communication device 22 according to the above-mentioned predetermined communication standard (for example, IEEE802.11ah).

[0061] The control unit 13 performs various information processing related to the wireless device 10. The control unit 13 is realized by, for example, a microcomputer, but may also be realized by a processor or a dedicated circuit. The functions of the control unit 13 are realized by hardware such as the microcomputer or processor constituting the control unit 13 executing a computer program (so-called software) stored in the storage unit 14.

[0062] The control unit 13 includes, as functional components, an acquisition unit 131, an estimation unit 132, a calculation unit 133, and a bandwidth limiting unit 134. Specific processes performed by the acquisition unit 131, the estimation unit 132, the calculation unit 133, and the bandwidth limiting unit 134 will be described later. The control unit 13 performs duty control (control based on the proportion (ratio) of transmittable time within the management unit time) using a management unit time shorter than the unit time (here, one hour). The management unit time is, for example, 60 seconds, but is not limited to this and may be set appropriately depending on the design. The management unit time is used as the duration of a first period ending at the current time and the duration of a second period starting at the current time. The following description will mainly focus on the case where the durations of the first period and the second period are equal, but the first period and the second period may have different durations.

[0063] The memory unit 14 is a storage device that stores computer programs and the like executed by the control unit 13. The memory unit 14 can also temporarily store information that needs to be stored due to information processing performed by the first communication unit 11, the second communication unit 12, and the control unit 13. The memory unit 14 is realized by, for example, an HDD (Hard Disk Drive), but may also be realized by a semiconductor memory.

[0064] The first communication device 21 transmits data to the second communication device 22 via the wireless device 10. For example, the first communication device 21 transmits data to the wireless device 10 in response to a request from the second communication device 22 obtained via the wireless device 10. At this time, the first communication device 21 transmits identification information of the second communication device 22 together with the data.

[0065] The first communication device 21 may adjust the communication speed of data that the first communication device 21 transmits to the wireless device 10 in accordance with a control signal output from the band limiting unit 134 of the wireless device 10, for example.

[0066] It should be noted that the communication between the first communication device 21 and the wireless device 10 has been explained in the first communication unit 11, and therefore the explanation thereof will be omitted here.

[0067] The wireless device 10 may be, for example, an access point (wireless access point) equipped with a wireless communication circuit, or may be a relay device (bridge device) that relays wired communication and wireless communication back and forth.

[0068] The first communication device 21 may be, for example, a web server, an edge server, or a sensor. The sensor may be, for example, a camera, a microphone, or a thermal image sensor, but is not particularly limited to such.

[0069] The second communication device 22 acquires data transmitted in accordance with a predetermined communication standard (IEEE802.11ah) from the wireless device 10. The second communication device 22 is, for example, an information terminal such as a stationary or portable computer device, a tablet terminal, or a smartphone.

[0070] [2. Operation] Next, the operation of the radio device 10 according to the present embodiment will be described. Fig. 5 is a flow diagram showing an example of processing executed by the radio device 10 according to the embodiment. Fig. 6 is a schematic diagram for explaining an example of the operation of the band limiting unit 134 in the band limiting step S4.

[0071] 5, in acquisition step S1, acquisition unit 131 of wireless device 10 acquires the time used by wireless device 10 to transmit data to second communication device 22 during a first period (e.g., the most recent 60 seconds) ending at the current time. For example, acquisition unit 131 may refer to the communication history stored in storage unit 14 and calculate the time used by second communication unit 12 to transmit data to second communication device 22 during the first period from the transmission record during the first period, or may read the time from storage unit 14.

[0072] In the acquisition step S1, the acquisition unit 131 may further acquire the time used for transmitting, for example, management frames during the first period. For example, the acquisition unit 131 may refer to the communication history stored in the storage unit 14 and calculate the time used by the second communication unit 12 to transmit management frames to the second communication device 22 from the transmission record during the first period, or may read out a predetermined time from the storage unit 14. Note that since the wireless device 10 always transmits a constant amount of management frames at the slowest data rate, the time used for transmitting management frames does not change during the first period or the second period, and therefore a predetermined fixed value may be used.

[0073] Next, in estimation step S2, the estimation unit 132 of the wireless device 10 uses the time used to transmit data to the second communication device 22 during the first period acquired in acquisition step S1 and the time used for management frames during a second period (e.g., the next 60 seconds) starting from the current time to estimate the time available for the wireless device 10 to transmit new data to the second communication device 22 during the second period so that the total wireless transmission time during the time period relative to the total time of the first and second periods does not exceed a predetermined time ratio (i.e., 10% in 802.11ah communication). For example, if the first and second periods have the same length of 60 seconds, the estimation unit 132 of the wireless device 10 can estimate the time available for the wireless device 10 to transmit new data to the second communication device 22 during the second period so that the sum of the wireless transmission time during the first period and the wireless transmission time during the second period is equal to or less than twice 6 seconds. In this way, even if radio transmission is carried out in a first period exceeding a predetermined time ratio, it can be reduced by that amount in the following second period, and conversely, if radio transmission is carried out in a first period below a predetermined time ratio, the surplus amount can be accumulated in the following second period to consume time for radio transmission, thereby enabling flexible operational management of transmission.

[0074] Next, in calculation step S3, calculation unit 133 of wireless device 10 calculates the communication bandwidth available for wireless device 10 to transmit new data to second communication device 22 during the second period by multiplying the time available for wireless device 10 to transmit new data to second communication device 22 during the second period, estimated in estimation step S2, by the data rate at the current time and then dividing the result by the length of the second period (60 seconds in this example).

[0075] Next, in a bandwidth limiting step S4, the bandwidth limiting unit 134 limits the bandwidth used by the wireless device 10 to transmit to the second communication device 22 during the second period, according to the communication bandwidth calculated in the calculation step S3. At this time, simply limiting the bandwidth used by the wireless device 10 to transmit to the second communication device 22 may result in data backlog in the wireless device 10 depending on the amount of data received from the first communication device 21. If the backlogged data exceeds the buffer capacity, relaying may fail. Therefore, the wireless device 10 limits the communication speed of new data acquired from the first communication device 21. For example, as shown in FIG. 6 , the bandwidth limiting unit 134 limits the communication bandwidth that the first communication unit 11 can use for communication with the first communication device 21. This depends on the communication protocol between the wireless device 10 and the first communication device 21, but can be achieved by, for example, controlling the timing at which the wireless device 10 sends an Ack signal in response to data reception, or the timing at which the wireless device 10 sends a data transmission request. Of course, as will be described later, control information may be transmitted to the first communication device 21 to limit transmission.

[0076] When the processing of the band limiting step S4 is completed and a fixed period (for example, 2 seconds) has elapsed, the processing returns to the acquisition step S1 again. Note that the return to the processing of step S1 may not be at a fixed period, but may be at every timing when data is transmitted to the second communication device 22.

[0077] In this way, by repeatedly executing a series of processes (steps S1 to S4), wireless device 10 can control communications so that the total transmission time per unit time from the start of radio wave transmission does not exceed a predetermined time ratio per unit time.

[0078] Needless to say, the communication bandwidth value calculated in step S3 is not necessarily applied as a fixed value during the second period, but is replaced with a newly calculated value if the process returns to step S3 from step S4 via steps S1 and S2 during the second period.

[0079] [Specific example of estimation process] Next, the estimation process performed by the wireless device 10 in estimation step S2 will be described in more detail. FIG. 7 is a first diagram specifically illustrating the estimation process performed by the wireless device 10 according to the embodiment. FIG. 8 is a second diagram specifically illustrating the estimation process performed by the wireless device 10 according to the embodiment. FIG. 9 is a third diagram specifically illustrating the estimation process performed by the wireless device 10 according to the embodiment. FIG. 10 is a fourth diagram specifically illustrating the estimation process performed by the wireless device 10 according to the embodiment. Note that, in this example, the communication standard between the wireless device 10 and the second communication device 22 is IEEE802.11ah. In IEEE802.11ah, the wireless transmission time per unit time (1 hour = 3,600 seconds) is limited to 360 seconds, which is 1 / 10 of that time.

[0080] 7 to 10, the horizontal axis of the graph indicates time (seconds) when the time when the wireless device 10 is turned on is set as time 0. The vertical axis of the graph indicates the remaining time as a percentage of the total time (6 seconds in this example) during which the wireless device 10 can transmit radio waves in the 920 MHz band within the management unit time (60 seconds in this example). The remaining time percentage is calculated by subtracting the time used by the wireless device 10 to transmit radio waves from the total time (6 seconds) during which the wireless device 10 can transmit radio waves in the 920 MHz band within the management unit time (60 seconds), and dividing the result by the total time available for transmission (6 seconds). In the drawings, a control frame A1 indicates a first period (60 seconds in this example) ending at the current time, and a control frame A2 indicates a second period (60 seconds in this example) starting at the current time. The height of the control frame along the vertical axis is set to 100% (i.e., equivalent to 6 seconds).

[0081] 7 to 10 indicate the percentage of time used by management frame transmission. Dotted vertical bars indicate the percentage of time used by past data transmission, and dashed vertical bars indicate the percentage of time used by data transmission from the present onwards. Management frames will be explained on the assumption that beacon frames are transmitted every 100 milliseconds as mentioned above, for a period of 3.3 milliseconds (i.e., 2 seconds of transmission time is consumed in 60 seconds).

[0082] FIG. 7 illustrates an example of processing that the wireless device 10 executes when the wireless device 10 is powered on.

[0083] When the wireless device 10 is powered on, the acquisition unit 131 of the wireless device 10, for example, refers to the communication history in the control frame A1 stored in the storage unit 14, and acquires the time (here, zero seconds) that the wireless device 10 used to transmit data to the second communication device 22 during the first period. The acquisition unit 131 also acquires the time (here, zero seconds) that the wireless device 10 used to transmit management frames during the first period.

[0084] Next, the estimation unit 132 of the wireless device 10 uses the time (zero seconds) used to transmit data to the second communication device 22 during the first period acquired by the acquisition unit 131 and the time T1 used for the management frame during the second period to estimate the time T2 that the wireless device 10 can use to transmit new data to the second communication device 22 during the second period so that the sum of the wireless transmission time during the first period and the wireless transmission time during the second period does not exceed 12 seconds (in this example, the time obtained by multiplying the total time of the first and second periods, 120 seconds, by a predetermined time ratio of 10%).

[0085] The time during which wireless device 10 can transmit radio waves in the 920 MHz band (6 seconds in this example) is equivalent to 10% of the management unit time (60 seconds in this example). Here, the time available for wireless device 10 to transmit new data to second communication device 22 in the second period is the remaining time (6-2=4 seconds) obtained by subtracting the time used for transmitting management frames (2 seconds) from the available transmission time of wireless device 10 in the second period (60 seconds) (6 seconds). Furthermore, since no transmission was performed during the past first period, the 10 seconds obtained by adding the 6 seconds that are the surplus available communication time during this period is considered to be the available period for data transmission in the second period.

[0086] In this case, if 10 seconds is expressed as the ratio of time T2 to the time that wireless device 10 can transmit radio waves in the 920 MHz band, then 10 seconds / 6 seconds × 100 ≈ 167%, which corresponds to the upper end position of T2 in the graph in FIG.

[0087] Next, with reference to FIG. 8, an example of processing that the wireless device 10 executes when 30 seconds have passed since the wireless device 10 was powered on will be described.

[0088] The acquisition unit 131 of the wireless device 10 refers to the communication history in the control frame A1 stored in the storage unit 14, and acquires the time (here, zero seconds) that the wireless device 10 used to transmit data to the second communication device 22 during the first period. The acquisition unit 131 also acquires the time T1 (two seconds) that the wireless device 10 used to transmit a management frame during the first period.

[0089] Next, the estimation unit 132 of the wireless device 10 estimates the time T2 available for the wireless device 10 to transmit new data to the second communication device 22 during the second period, using the time acquired by the acquisition unit 131 (no data was transmitted for 30 seconds from the time the power was turned on, so that this is zero seconds) and the time T1 used for the management frame for the total of 120 seconds for the first and second periods (2 seconds per 60 seconds, so that the total of the first and second periods is 3 seconds). This time T2 is calculated so that the total of the wireless transmission time during the first period and the wireless transmission time during the second period does not exceed 12 seconds (the total of 120 seconds for the first and second periods multiplied by the predetermined time ratio of 10%). In the example of FIG. 8 , the time used for transmitting data to the second communication device 22 during the first period is zero seconds, so the time T2 available for the wireless device 10 to transmit new data to the second communication device 22 is 6 × 2 − 3 = 9 seconds. This corresponds to 9 / 6 = 150% of the length of the dashed line in FIG. 8 .

[0090] In the second period, the time T2 available for data transmission can be more generally expressed as follows: T2 = duration of period × 2 × α-Tm-Td This can be expressed as:

[0091] where T2 is the time available for data transmission in the second period, α is a predetermined time ratio, which is 10% in the 802.11ah standard, Tm is the management frame transmission time (the sum of the time for the first and second periods), and Td is the time used for data transmission in the first period.

[0092] The above formula is for the case where the first period length is equal to the second period length, but if the two are different, T2=(t1+t2)×α-Tm-Td Here, t1 is the length of the first period, and t2 is the length of the second period.

[0093] Once the time T2 available for data transmission in the second period has been estimated in this way, T2 is then multiplied by the data rate to calculate the amount of data that can be transmitted in the second period, and this is then divided by the length of the second period, which is 60 seconds, to obtain the transmission bandwidth for that period (in other words, the maximum bandwidth that can be transmitted).

[0094] That is, Transmission bandwidth (bps) = available time (sec) x data rate (bit / sec) / period length (sec) It is expressed as:

[0095] 9 illustrates an example of processing that the wireless device 10 executes when 60 seconds have passed since the wireless device 10 was powered on. In FIG. 9, the wireless device 10 starts transmitting data to the second communication device 22 30 seconds after the power was turned on.

[0096] The acquisition unit 131 of the wireless device 10 acquires the time T3 that the wireless device 10 used to transmit data to the second communication device 22 during the first period (0 to 60 seconds). At this time, the acquisition unit 131 also acquires the time T1 that the wireless device 10 used to transmit management frames during the first period.

[0097] Next, the estimation unit 132 of the wireless device 10 estimates the time T21 that the wireless device 10 can use to transmit new data to the second communication device 22 during the second period, using the time T3 used to transmit data to the second communication device 22 during the first period and the time T1×2 used to transmit management frames during the first and second periods (0 to 120 seconds), both acquired by the acquisition unit 131, so that the sum of the wireless transmission time during the first period and the wireless transmission time during the second period does not exceed 12 seconds (the total time of the first and second periods, 120 seconds, multiplied by a predetermined time ratio of 10%). Specifically, T21=6×2−2×2−T3. This can also be considered to mean that the estimation unit 132 can add the surplus bandwidth B1 that was unused during the period (0 to 30 seconds) during the first period when no data was transmitted to the second communication device 22 as the bandwidth B2 that can be used during the next management unit time (i.e., the second period). As shown in the example in Figure 9, in the case where 100% transmission, including management frames, has occurred from the past 30 seconds to the present, T3 = 2 seconds, and according to the above formula, T21 = 6 seconds, so the height of the dashed line in the figure is 100% (if the 2 seconds for management frames are included, it becomes (6 + 2) / 6 x 100 = 133%).

[0098] FIG. 10 illustrates an example of processing that the wireless device 10 executes when 90 seconds have passed since the wireless device 10 was powered on.

[0099] The acquisition unit 131 of the wireless device 10 acquires the time T3 that the wireless device 10 used to transmit data to the second communication device 22 during the first period (30 seconds to 90 seconds). At this time, the acquisition unit 131 also acquires the time T1 that the wireless device 10 used to transmit management frames during the first period.

[0100] Next, the estimation unit 132 of the wireless device 10 uses the time T3 used to transmit data to the second communication device 22 in the first period acquired by the acquisition unit 131 and the time T1 used for the management frame in the first period and the second period (30 seconds to 150 seconds) to estimate the time T22 that the wireless device 10 can use to transmit new data to the second communication device 22 in the second period so that the sum of the wireless transmission time in the first period and the wireless transmission time in the second period does not exceed 12 seconds (the total time of the first and second periods, 120 seconds, multiplied by a predetermined time ratio of 10%). Specifically, using the same calculation formula as that described in FIG. T22=6×2-2×2-T3 However, for example, if the time (6 seconds) during which wireless device 10 can transmit radio waves in the first period is used 100%, including the management frame, the estimation unit 132 can estimate that the time T22 during which wireless device 10 can transmit new data to second communication device 22 in the second period is the same as time T3. (When T3 = 4 seconds in the above formula, the actual transmission time during the first period is 6 seconds, but when substituted into the above formula, T22 also becomes 4 seconds, and as shown in FIG. 10, including the 2 seconds for the management frame, the graph becomes 6 seconds, i.e., 100% high.)

[0101] Thereafter, the transmission bandwidth for the second period (90 seconds to 150 seconds) is calculated using the same procedure as described in the explanation of FIG.

[0102] In the above example, in the band limiting step S4, the band limiting unit 134 of the wireless device 10 limits the communication speed of the data that the wireless device 10 acquires from the first communication unit 11 in accordance with the communication band calculated in the calculation step S3, but this is not limiting. For example, as shown in Fig. 11, the band limiting unit 134 of the wireless device 10 may limit the communication speed of the data that the first communication device 21 transmits to the wireless device 10 in accordance with the communication band calculated in the calculation step S3.

[0103] 11 is a schematic diagram illustrating another example of the operation of the band limiting unit 134 in the band limiting step S4. First, for example, the band limiting unit 134 outputs to the first communication unit 11 control information including the communication band available for wireless device 10 to transmit to the second communication device 22, calculated in the calculation step S3, and an instruction to cause the first communication device 21 to limit the transmission rate of data transmitted to the wireless device 10 in accordance with the communication band. Here, the instruction included in the control information may include, for example, the transmission rate of data transmitted to the wireless device 10, calculated by the band limiting unit 134 of the wireless device 10. The data transmission rate may be calculated based on a predetermined priority for using the communication band, among the communication bands calculated in the calculation step S3, that the wireless device 10 can use to transmit to the second communication device 22. Specifically, the data transmission rate may be determined based on a predetermined allocation ratio (e.g., 80:20) between the communication band available for wireless device 10 to transmit to the second communication device 22 and the data transmission rate. Next, upon acquiring the control information output from the bandwidth limiting unit 134, the first communication unit 11 transmits the control information to the first communication device 21. The first communication device 21 determines the transmission rate of the data to be transmitted to the wireless device 10 based on the instruction included in the control information transmitted from the wireless device 10.

[0104] As described above, in the embodiment of the present invention, wireless device 10 obtains the time used for transmitting data to second communication device 22 during a first period ending at the current time from the actual transmission record with second communication device 22 during the first period, estimates the time available for transmitting new data to second communication device 22 during the next control cycle (more specifically, the second period starting at the current time) so that the sum of the wireless transmission times during the first and second periods does not exceed a predetermined time ratio to the total time of the first and second periods, and calculates the communication bandwidth available for transmitting new data to second communication device 22 by multiplying the estimated time by the data rate. As a result, even if the data rate fluctuates depending on the state of wireless communication, wireless device 10 can calculate the communication bandwidth available for communication with second communication device 22 in accordance with the fluctuations in the data rate. Therefore, wireless device 10 can perform appropriate communication control in accordance with changes in the wireless environment.

[0105] Furthermore, in the embodiment of the present invention, wireless device 10 further (i) limits the communication speed of new data acquired from first communication device 21 during the second time period, or (ii) limits the communication speed of new data transmitted from first communication device 21 to wireless device 10 during the second time period, according to the calculated communication bandwidth. By the above (i), wireless device 10 can limit the amount of new data acquired from first communication device 21 to the amount that can be transmitted to second communication device 22 within the available time for transmission. By the above (ii), wireless device 10 can limit the amount of new data transmitted from first communication device 21 to the amount that can be transmitted to second communication device 22 within the available time for transmission. By the above (i) or (ii), wireless device 10 can appropriately control communication in accordance with changes in the wireless environment in communication system 1.

[0106] In the above embodiment, the wireless device 10 and the first communication device 21 are separate devices. However, this is not necessarily limited to this example. For example, the wireless device 10 may include the first communication device 21. These two devices may share the same housing and may be arranged on the same board. Furthermore, for example, the first communication device 21 may be attached to the housing of the wireless device 10. For example, the first communication unit 11 of the wireless device 10 may transmit and receive data to and from the first communication device 21 via communication or without communication. For example, if the first communication device 21 is attached to the housing of the wireless device 10, the first communication unit 11 of the wireless device 10 may transmit and receive data to and from the first communication device 21 via wired communication or wireless communication. Furthermore, for example, if the first communication device 21 is built into the housing of the wireless device 10, the first communication unit 11 is connected to the first communication device 21 via an internal bus.

[0107] 12 is a schematic diagram illustrating an example of the operation of the band limiting unit 134 when the first communication device 21 is integrated with the wireless device 10 and the wireless device 10 includes the first communication device 21. For example, as shown in FIG. 12, the band limiting unit 134 of the wireless device 10 outputs to the first communication unit 11 control information including the communication band that the wireless device 10 can use to transmit new data to the second communication device 22, calculated in calculation step S3, and an instruction to cause the first communication device 21 to control the transmission rate of the new data to be transmitted to the wireless device 10 in accordance with the communication band. Next, the first communication unit 11 transmits the control information acquired from the band limiting unit 134 to the first communication device 21. Note that the control information does not necessarily have to include the above-mentioned instruction. Note that the control information includes identification information of the wireless device 10 and the second communication device 22.

[0108] In the above embodiment, even if the wireless data rate with the second communication device 22 changes dynamically depending on the error rate, the wireless device 10 calculates the bandwidth available for transmitting new data to the second communication device 22 using the data rate at the current time, and therefore can perform appropriate communication control in response to changes in the wireless environment. However, the data rate used to calculate the bandwidth available for the second communication device 22 may be fixed to a value lower than normal. This allows the wireless device 10 to perform stable data communication regardless of the wireless environment.

[0109] When the wireless device 10 transmits new data to a plurality of second communication devices 22, the bandwidth available for transmitting the new data may be further limited, for example, to 10% to 5%, depending on the number of second communication devices 22. This makes it possible to increase the number of second communication devices 22 that can simultaneously communicate in the same frequency band (for example, the 920 MHz band).

[0110] (Application example of embodiment) For example, a known technology measures the available communication bandwidth before transmitting a video, and then determines and transmits the compression rate of the video. In a communication system using such conventional technology, the communication device transmitting the video (e.g., a content provider communication device) unilaterally determines the compression rate of the video and distributes the video. Therefore, if the communication environment subsequently deteriorates, the quality of the video received by the receiving communication device (e.g., a content viewer communication device) may significantly deteriorate. This can cause discomfort to viewers each time the compression rate of the transmitting communication device changes. Furthermore, when video is distributed using a communication standard (e.g., 802.11ah) that imposes a limit on the total transmission time per unit time, as described above, the distribution may stop when the upper limit of the limit is reached, and the video cannot be distributed until the communication is restored (i.e., until the communication is available again). The wireless device according to the embodiment of the present invention can be applied to address such issues.

[0111] An example of an application of the embodiment of the present invention is a communication system (also called a video distribution system) that distributes video from a content server to a plurality of communication terminals connected via a network.

[0112] The following describes the configuration of a video distribution system including a wireless device according to an application example of an embodiment of the present invention. Fig. 13 is a schematic diagram showing an example of the configuration of a video distribution system including a wireless device according to an embodiment of the present invention.

[0113] In the application example of this embodiment shown in Fig. 13, video distribution system 1000 includes, for example, wireless device 100, distribution server 301 (corresponding to first communication device 21 in the embodiment of the present invention), communication terminal 201 (corresponding to second communication device 22 in the embodiment of the present invention), communication terminal 202 (corresponding to another second communication device 22 in the embodiment of the present invention), communication link 303, and wireless link 304. Note that Fig. 13 shows an example in which video distribution system 1000 includes two communication terminals, communication terminal 201 and communication terminal 202, but it may include three or more communication terminals.

[0114] The distribution server 301 performs compression processing on the video data and transmits the compressed video data to the wireless device 100 .

[0115] Wireless device 100 sets the compression rate for the compression process of distribution server 301 in the second period according to the communication bandwidth calculated by calculation unit 133 , and transmits the set compression rate to distribution server 301 .

[0116] Specifically, in the process of receiving video data from distribution server 301, wireless device 100 according to an application example of the present invention calculates the transmission bandwidth through the steps shown in FIG. 5 described above, and then transmits the obtained control information to distribution server 301. Based on the control information, distribution server 301 can dynamically change the compression rate of the video data to be distributed. More specifically, distribution server 301 can dynamically change the compression process used in video encoding or audio encoding, and transmits the video data by performing video encoding or audio encoding using the changed compression process. Based on the control information received from wireless device 100, distribution server 301 compresses the video data at an appropriate compression rate, thereby generating video data to be transmitted to communication terminals 201 and 202 so as to comply with the transmission time limit from wireless device 100 to the communication terminals.

[0117] When the distribution server 301 transmits video data to the communication terminals 201 and 202 via the wireless link 304, the transmission time of the video data from the wireless device 100 to the communication terminals 201 and 202 via the wireless link 304 is automatically controlled based on the amount of data received from the distribution server 301.

[0118] This is because the video data distributed from the distribution server 301 is generated in advance by being compressed at an appropriate compression rate based on the control information received from the wireless device 100, and the data volume itself is an appropriate data volume that can be communicated via the wireless link 304.

[0119] In this way, the wireless device 100 according to the application example of the embodiment of the present invention can perform appropriate communication control in response to changes in the wireless environment.

[0120] The present invention can be realized not only as an apparatus, but also as a method in which the processing means constituting the apparatus are steps, as a program that causes a computer to execute those steps, as a computer-readable recording medium such as a CD-ROM on which the program is recorded, or as information, data, or signals that represent the program.These programs, information, data, and signals may be distributed via a communication network such as the Internet.

[0121] While the wireless device, the control method for the wireless device, and the program of the present invention have been described above based on the embodiments, the present invention is not limited to these embodiments. As long as they do not deviate from the spirit of the present invention, various modifications that a person skilled in the art would conceive of to the present embodiments and configurations constructed by combining components of different embodiments are also included within the scope of the present invention. [Industrial Applicability]

[0122] The present invention can be used in wireless devices and the like that can perform appropriate communication control in response to changes in the wireless environment. [Explanation of symbols]

[0123] 1. Communication Systems 10, 100 wireless devices 11 First Communications Department 12 Second Communications Department 13 Control Unit 131 Acquisition Department 132 Estimation Department 133 Calculation Unit 134 Bandwidth limiting section 14 Storage section 21 First communication device 22 Second communication device 201, 202 communication terminal 301 Distribution Server 303 Communication Links 304 Wireless Link 1000 Video Distribution System A1, A2 control frame B1 and B2 bands

Claims

1. A wireless device that transmits data acquired from a first communication device to a second communication device using a predetermined communication standard, the predetermined communication standard limits the wireless transmission time per unit time to a predetermined time ratio or less, The wireless device an acquisition unit that acquires a time used by the wireless device to transmit the data to the second communication device and a time used by the wireless device to transmit a management frame during a first period ending at a current time; an estimation unit that estimates a time that the wireless device can use to transmit new data to the second communication device during the second period, using the time used to transmit the data, the time used to transmit the management frame, and the time used to transmit the management frame during a second period starting from the current time, so that the sum of the wireless transmission time during the first period and the wireless transmission time during the second period does not exceed the predetermined time ratio with respect to the total time of the first period and the second period; a calculation unit that calculates a communication bandwidth that the wireless device can use to transmit the new data to the second communication device during the second period by multiplying a time that can be used to transmit the new data by a data rate that is a communication speed between the wireless device and the second communication device; and Equipped with Radio equipment.

2. further comprising a band limiting unit that limits a communication speed of data that the wireless device acquires from the first communication device during the second period in accordance with the communication band calculated by the calculation unit.

10. The wireless device of claim 1.

3. further comprising a bandwidth limiting unit that transmits to the first communication device control information including an instruction to limit a communication rate of the new data that the first communication device transmits to the wireless device during the second period, in accordance with the communication bandwidth calculated by the calculation unit.

10. The wireless device of claim 1.

4. The first period and the second period have the same time length. The wireless device according to any one of claims 1 to 3.

5. the wireless device includes the first communication device; The wireless device according to any one of claims 1 to 3.

6. The predetermined communication standard is IEEE 802.11ah. The wireless device according to any one of claims 1 to 3.

7. 1. A communication system comprising: A communication system comprising: the wireless device according to claim 1; and the first communication device; the first communication device performs a compression process on the moving image data and transmits the compressed moving image data as the data; The wireless device sets a compression rate in the compression process of the first communication device during the second period in accordance with the communication bandwidth calculated by the calculation unit, and transmits the set compression rate to the first communication device. Communication system.

8. A method for controlling a wireless device that transmits data acquired from a first communication device to a second communication device using a predetermined communication standard, the predetermined communication standard limits the wireless transmission time per unit time to a predetermined time ratio or less, The wireless device an acquisition step of acquiring a time used by the wireless device to transmit the data to the second communication device and a time used by the wireless device to transmit a management frame during a first period ending at a current time; an estimation step of estimating a time available for the wireless device to transmit new data to the second communication device in the second period, using the time used for transmitting the data, the time used for transmitting the management frame, and the time used for transmitting the management frame in a second period starting from the current time, so that the sum of the wireless transmission time in the first period and the wireless transmission time in the second period does not exceed the predetermined time ratio with respect to the total time of the first period and the second period; a calculation step of multiplying a time available for transmitting the new data by a data rate that is a communication speed between the wireless device and the second communication device to calculate a communication bandwidth that the wireless device can use to transmit the new data to the second communication device during the second period; Including, A method for controlling a wireless device.

9. A program that causes one or more computers to execute the method for controlling a wireless device according to claim 8.

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