Wireless communication device and wireless communication method

Abstract

A wireless communication device according to one embodiment of the present invention is equipped with a wireless communication module capable of performing wireless communication using a second channel with no restrictions on a total transmission time rate, and is characterized by comprising: a first transmission control unit that, when transmitting data frames using the second channel, performs control of transmitting a frame that has an expected channel occupancy period longer than a time required for transmitting data frames in a transmission queue; and a second transmission control unit that performs control of transmitting the data frames in the transmission queue using the second channel after the first transmission control unit has performed control of transmitting the frame that has the expected channel occupancy period.

Description

[Technical Field]

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

[0002] With the development of IoT (Internet of Things) wireless communications, there is a need to transmit not only sensor data but also image data and large volumes of data over wide wireless areas. For example, the 920 MHz band is being broadened and transmission capacity is being expanded through revisions to domestic laws and regulations.

[0003] However, the 920 MHz band has a total transmission time rate (a limit on the total transmission time per hour) of 10%, which means that the amount of data that a single terminal can transmit can be significantly less than the actual performance of the radio.

[0004] However, the limit on the total transmission time rate is a regulation for the shared band between active tags (wireless communication terminals such as sensor communication systems that transmit and receive by sensing the carrier before transmitting). There is no limit on the total transmission time rate for the priority band of passive tags (wireless communication terminals of electronic tag systems such as RFID that do not transmit radio waves themselves but return a response to transmitted radio waves). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] IEEE Standard for Information Technology-Telecommunications and Information Exchange between Systems Local and Metropolitan Area Networks- Specific Requirements, Part 11: Wireless LAN Medium Access Control(MAC) and Physical Layer (PHY) Specifications, IEEE Computer Society, Developed by the LAN / MAN Standards Committee, IEEE Std 802.11-2020 (Revision of IEEE Std 802.11-2016), Approved 3 December 2020, IEEE SA Standards Board [Non-patent document 2] "920MHz-BAND TELEMETER, TELECONTROL AND DATA TRANSMISSION RADIO EQUIPMENT", ARIB STANDARD, ARIB STD-T108 Version 1.4, Established February 14, 2012, Revised April 23, 2021, Association of Radio Industries and Businesses Summary of the Invention [Problem to be solved by the invention]

[0006] Although there is no limit on the total transmission time rate for the passive tag priority band, the carrier sense time before transmission is specified to be 5 msec or more, which is significantly longer than the carrier sense time (128 μsec or more) for the active tag shared band.

[0007] Furthermore, the passive tag priority band requires a 50 msec pause after the radio wave is emitted (the time to stop transmission of anything other than response signals such as ACK) (see Non-Patent Document 2). However, once a carrier sense of 5 msec or more is performed in the passive tag priority band, there is no pause and the carrier sense time is 128 μsec, as long as it is within 4 seconds of the initial radio wave emission.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a wireless communication device and a wireless communication method that can improve frequency utilization efficiency even in channels with long specified downtimes or carrier sense times. [Means for solving the problem]

[0009] A wireless communication device according to one embodiment of the present invention is a wireless communication device equipped with a wireless communication module that enables wireless communication using a second channel that has no limit on the total transmission time rate and that has a longer pause time for suspending transmissions other than response signals and a longer carrier sense time before transmission than a first channel that has a limit on the total transmission time rate, and is characterized by having a first transmission control unit that controls the transmission of a frame including a planned channel occupancy period that is longer than the time required to transmit a data frame in a transmission queue when transmitting a data frame via the second channel, and a second transmission control unit that controls the transmission of the data frame in the transmission queue via the second channel after the first transmission control unit has controlled the transmission of a frame including the planned channel occupancy period.

[0010] Furthermore, a wireless communication method according to one embodiment of the present invention is a wireless communication method performed by a wireless communication device having a wireless communication module that is enabled to perform wireless communication using a second channel that has no limit on the total transmission time rate and that has a longer pause time for suspending transmissions other than response signals and a longer carrier sense time before transmission than a first channel that has a limit on the total transmission time rate, and is characterized in that when transmitting a data frame via the second channel, the method includes a first transmission control step of controlling to transmit a frame that includes a planned channel occupancy period that is longer than the time required to transmit a data frame in a transmission queue, and a second transmission control step of controlling to transmit the data frame in the transmission queue via the second channel after controlling to transmit a frame that includes the planned channel occupancy period. [Effects of the Invention]

[0011] According to the present invention, it is possible to improve frequency utilization efficiency even in a channel with a long specified downtime or carrier sense time. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 illustrates an example of the configuration of a wireless communication device according to an embodiment. [Figure 2] FIG. 10 is a diagram showing combinations of parameters for transmission time restrictions in each frequency band of the 920 MHz band. [Figure 3] FIG. 1 is a diagram showing channels and center frequencies of a passive tag priority band in the 920 MHz band. [Figure 4] FIG. 10 is a diagram illustrating the format of a CTS-to-self. [Figure 5] 10 is a diagram illustrating timings at which a wireless communication device according to an embodiment transmits a transmission frame in a passive tag priority band. [Figure 6] FIG. 10 is a diagram showing transmission timing when multiple wireless communication devices interrupt even within the transmission time limit. [Figure 7] FIG. 1 illustrates the timing of burst transmission using CTS-to-self. [Figure 8] 10 is a flowchart illustrating a process performed by a wireless communication device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] A wireless communication device according to an embodiment will be described below with reference to the drawings. Fig. 1 is a diagram showing an example of the configuration of a wireless communication device 1 according to an embodiment. As shown in Fig. 1, the wireless communication device 1 according to an embodiment includes, for example, a memory 10, a drive 11, a timer 12, a user interface 13, a wired communication module 14, a first wireless communication module 15-1, a second wireless communication module 15-2, and a control circuit 16, which are connected via a bus 17.

[0014] The memory 10 is a storage device that stores, for example, a control program 100 and management information 102. The drive 11 reads and writes data from and to a storage medium 110. The timer 12 measures the time when the wireless communication device 1 performs control. The user interface 13 is an input / output device that includes, for example, a keyboard and a display.

[0015] The wired communication module 14 is a module that performs wired communication with other devices. The first wireless communication module 15-1 and the second wireless communication module 15-2 each have a different NIC, and each perform wireless communication with other devices using a different channel.

[0016] The first wireless communication module 15-1 performs wireless communication using, for example, a passive tag priority band (see FIG. 2). The second wireless communication module 15-2 performs wireless communication using, for example, an active tag shared band (see FIG. 2). The wireless communication device 1 may not necessarily be provided with the second wireless communication module 15-2.

[0017] The control circuit 16 includes a CPU 160, a first transmission control unit 162, and a second transmission control unit 164, and controls the components of the wireless communication device 1. For example, the control circuit 16 performs control using the time measured by the timer 12.

[0018] For example, when transmitting a data frame over a channel using a passive tag priority band, the first transmission control unit 162 controls the transmission of a frame that includes a planned channel occupancy period that is longer than the time required to transmit the data frames in the transmission queue.

[0019] After the first transmission control unit 162 has controlled the transmission of a frame including the planned channel occupancy period, the second transmission control unit 164 controls the transmission of data frames in the transmission queue over a channel of the passive tag priority band. The second transmission control unit 164 also controls the transmission of bursts over a channel that uses the passive tag priority band.

[0020] Figure 2 shows the combination of parameters for transmission time limits in each frequency band in the 920 MHz band. Figure 3 shows the channels and center frequencies of the passive tag priority band in the 920 MHz band. (A) in Figure 2 shows the parameters of the passive tag priority band. (B) in Figure 2 shows the parameters of the active tag shared band.

[0021] The passive tag priority band is a channel with no limit on the total transmission time rate. In the passive tag priority band, the carrier sense time is specified to be long so that the passive tag operation is not hindered by the transmission of the active tag, and a pause time is provided.

[0022] Specifically, the passive tag priority band is stipulated to have a carrier sense time of 5 msec or more before transmission, and a pause time of 50 msec or more after the radio wave is emitted during which transmissions other than response signals are stopped. Note that once a carrier sense of 5 msec or more is performed, the passive tag priority band does not require a pause time as long as it is within 4 seconds of the initial radio wave emission, and the carrier sense time is also stipulated to be 128 μsec.

[0023] The active tag shared band is a channel with a limit on the total transmission time rate. Specifically, the active tag shared band has a limit of 10% or less, and the carrier sense time before transmission is set to 128 μsec. In other words, the active tag priority band has a limit of 360 seconds per hour for the total transmission time, which can make large-volume communication difficult.

[0024] In other words, channels using the passive tag priority band have longer pause times during which transmissions other than response signals are stopped, and longer carrier sense times before transmission, so there are no restrictions on the total transmission time rate, compared to channels using the active tag shared band, which have restrictions on the total transmission time rate. Furthermore, the passive tag priority band does not have these restrictions for 4 seconds after the radio wave is emitted after a carrier sense of 5 msec or more, allowing for efficient transmission.

[0025] For example, when transmitting using a passive tag priority band, the wireless communication device 1 transmits packets in the transmission queue all at once by explicitly declaring use for a certain period of time. This allows the wireless communication device 1 to transmit efficiently even in a band with a long pause time.

[0026] The declaration of a certain usage period is performed by transmitting a frame including a planned occupancy period, etc. For example, in the case of the IEEE 802.11 standard (the current standard for the sub-1 GHz MHz band is IEEE 802.11ah), the wireless communication device 1 protects the transmission period by using CTS-to-self (Clear To Send to self), TWT (Target Wake Time), and RAW (Restrict Access Window).

[0027] The CTS-to-self, which explicitly protects the transmission period, has the same format as the CTS frame, as shown in Fig. 4. Furthermore, the wireless communication device 1 may specify the planned occupancy period to each wireless terminal in a polling format (or TWT) from the base station, or may specify the planned occupancy period only for a specific wireless terminal and traffic.

[0028] 5 is a diagram showing the timing at which the wireless communication device 1 according to an embodiment transmits a transmission frame in the passive tag priority band. IEEE 802.11ah is one of the wireless communication standards used in the sub-1 GHz band. In IEEE 802.11ah, the time length of a wireless communication frame is 28 msec.

[0029] The frequency efficiency is better when the wireless communication device 1 performs continuous transmission by itself than when it competes with other devices for the passive tag priority band.

[0030] 6 is a diagram showing transmission timing when multiple wireless communication devices interrupt even within the transmission time limit. For example, if a wireless communication terminal that has acquired the transmission right transmits a wireless communication frame waits 5 msec or more before transmitting again, another wireless communication terminal will interrupt the transmission time limit. In this case, even if subsequent packets to be transmitted arrive frequently, the opportunity to transmit again will be significantly delayed compared to when there is no interruption.

[0031] Therefore, the wireless communication device 1 can improve frequency utilization efficiency by performing burst transmission as much as possible in frequency bands with long pause times and carrier sense times.When declaring the usage time of the passive tag priority band, the wireless communication device 1 specifies a period longer than the period actually required for transmission at that time, so that packets that arrive in the transmission queue while transmitting can be transmitted without interruption.

[0032] Figure 7 shows the timing of burst transmission using CTS-to-self, a wireless communication frame that notifies surrounding terminals (IEEE 802.11 standard) of the terminal's own transmission before transmitting a data packet.

[0033] The frame contents include a planned occupancy period (the period during which surrounding terminals are prohibited from transmitting: NAV), which can be set up to approximately 32 msec.

[0034] After the wireless communication device 1 sets the carrier sense time to 5 msec or more, if it is known that transmission traffic is constantly present and packets will be generated in the transmission queue from the time when the first wireless communication frame is transmitted after obtaining a transmission opportunity until the transmission time limit of 4 s is completed, the wireless communication device 1 sets the transmission period within CTS-to-self to a longer time than the time length of the actual wireless communication frame.

[0035] In this way, by setting a long expected occupancy period, the wireless communication device 1 temporarily runs out of packets in the transmission queue, and even if a situation arises where a surrounding wireless terminal can interrupt, the surrounding terminal cannot interrupt because the NAV is set.

[0036] Then, the wireless communication device 1 can transmit packets generated during that time after the next carrier sense time (128 μsec or more if within the transmission time limit). Furthermore, even if a large number of packets are generated in the transmission queue after that, the wireless communication device 1 can transmit them in bursts within a short carrier sense time, thereby improving frequency utilization efficiency.

[0037] Furthermore, even if there are no more packets to be transmitted in the transmission queue, once NAV is complete, wireless communication device 1 can transmit CTS-to-self or other action frames, control frames (such as ACKs to management frames), or management frames (such as beacon frames or association frames), thereby enabling subsequent transmission without being interrupted by surrounding wireless communication terminals.

[0038] Furthermore, the wireless communication device 1 sets a packet generation source (such as ping) in an upper layer so that packets are generated periodically in the transmission queue, and encourages transmission within a range that does not affect the original communication.

[0039] However, if the wireless communication device 1 determines that there are enough packets in the transmission queue (for example, using the results of observation by packet monitoring at the TCP layer), it stops generating redundant packets.

[0040] Alternatively, the wireless communication device 1 may control RAW and TWT to apply a period of time during which transmission is prohibited for each timing other than the burst transmission timing of each wireless communication terminal, thereby realizing burst transmission by making it possible for only the wireless communication terminal at the transmission timing to transmit.

[0041] Fig. 8 is a flowchart showing an example of the operation of the wireless communication device 1. As shown in Fig. 8, the wireless communication device 1 transmits a CTS-to-self with a longer NAV period (S100).

[0042] Next, the wireless communication device 1 determines whether or not a data frame to be transmitted exists in the transmission queue (S102). If the wireless communication device 1 determines that a data frame to be transmitted exists in the transmission queue (S102: Yes), the wireless communication device 1 proceeds to processing of S104, and if the wireless communication device 1 determines that a data frame to be transmitted does not exist in the transmission queue (S102: No), the wireless communication device 1 proceeds to processing of S106.

[0043] In step 104 (S104), the wireless communication device 1 transmits a data frame. In step 106 (S106), the wireless communication device 1 transmits other frames.

[0044] Next, the wireless communication device 1 determines whether the NAV period has not completed (S108). If the wireless communication device 1 determines that the NAV period has not completed (S108: Yes), the wireless communication device 1 returns to the processing of S102, and if the wireless communication device 1 determines that the NAV period has completed (S108: No), the wireless communication device 1 proceeds to the processing of S110.

[0045] Then, the wireless communication device 1 determines whether the transmission time limit period has not expired (S110). If the wireless communication device 1 determines that the transmission time limit period has not expired (S110: Yes), the wireless communication device 1 returns to the process of S100, and if the wireless communication device 1 determines that the transmission time limit period has expired (S110: No), the wireless communication device 1 ends the process.

[0046] In this way, the wireless communication device 1 according to one embodiment transmits a frame including a planned channel occupancy period that is longer than the time required to transmit the data frames in the transmission queue, and then transmits the data frames in the transmission queue on a channel that has no limit on the total transmission time rate. This allows for increased frequency utilization efficiency even in channels with long specified downtimes or carrier sense times.

[0047] In addition, each function of the wireless communication device 1 may be configured, in part or in whole, by hardware such as a PLD (Programmable Logic Device) or an FPGA (Field Programmable Gate Array), or may be configured as a program executed by a processor such as a CPU.

[0048] For example, the wireless communication device 1 according to the present invention can be realized using a computer and a program, and the program can be recorded on a storage medium or provided via a network. [Explanation of symbols]

[0049] 1 wireless communication device, 10 memory, 12 timer, 13 user interface, 14 wired communication module, 15-1 first wireless communication module, 15-2 second wireless communication module, 16 control circuit, 17 bus, 100 control program, 102 management information, 110 storage medium, 160 CPU, 162 first transmission control unit, 164 second transmission control unit

Claims

1. A wireless communication device including a wireless communication module that enables wireless communication using a second channel that has no limit on the total transmission time rate and that has a specified idle time during which transmissions other than response signals are stopped and a specified carrier sense time before transmission that are longer than those of a first channel that has a limit on the total transmission time rate, a first transmission control unit that controls, when transmitting a data frame through the second channel, to transmit a frame including a planned channel occupancy period that is longer than the time required to transmit the data frame in the transmission queue; a second transmission control unit that controls the first transmission control unit to transmit a frame including a planned channel occupancy period, and then controls the data frame in the transmission queue to be transmitted via the second channel; A wireless communication device comprising:

2. The first channel is A channel using the active tag shared band, The second channel is The channel must use the passive tag priority band.

2. The wireless communication device according to claim 1,

3. The active tag shared band is The total transmission time rate is specified to be 10% or less, and the carrier sense time before transmission is specified to be 128 μsec. The passive tag priority band is: The carrier sense time before transmission is specified to be 5 msec or more, the pause time for stopping transmission other than the response signal is specified to be 50 msec or more from the emission of radio waves, and once a carrier sense of 5 msec or more has been performed, the pause time is not required as long as it is within 4 seconds from the first emission of radio waves, and the carrier sense time is also specified to be 128 μsec.

3. The wireless communication device according to claim 2, wherein:

4. The second transmission control unit Controlling burst transmission over the second channel.

4. The wireless communication device according to claim 1, wherein:

5. A wireless communication method performed by a wireless communication device having a wireless communication module that enables wireless communication using a second channel in which a pause time during which transmissions other than response signals are stopped and a carrier sense time before transmission are specified to be longer than those of a first channel in which a total transmission time rate is limited, and in which no total transmission time rate is limited, a first transmission control step of controlling transmission of a data frame through the second channel so as to transmit a frame including a planned channel occupancy period longer than a time required to transmit the data frame in the transmission queue; a second transmission control step of controlling the transmission of a frame including a planned channel occupancy period, and then controlling the transmission of a data frame in a transmission queue via the second channel; A wireless communication method comprising:

6. The first channel is A channel using the active tag shared band, The second channel is The channel must use the passive tag priority band.

6. The wireless communication method according to claim 5,

7. The active tag shared band is The total transmission time rate is specified to be 10% or less, and the carrier sense time before transmission is specified to be 128 μsec. The passive tag priority band is: The carrier sense time before transmission is specified to be 5 msec or more, the pause time for stopping transmission other than the response signal is specified to be 50 msec or more from the emission of radio waves, and once a carrier sense of 5 msec or more has been performed, the pause time is not required as long as it is within 4 seconds from the first emission of radio waves, and the carrier sense time is also specified to be 128 μsec.

7. The wireless communication method according to claim 6, wherein:

8. In the second transmission control step, Controlling burst transmission over the second channel. The wireless communication method according to any one of claims 5 to 7,

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