Wireless communication device and control method

Abstract

One embodiment of the present invention pertains to a wireless communication device comprising: a carrier sensing unit that performs carrier sensing prior to transmission of a signal for a host transmission channel and also performs carrier sensing prior to signal transmission for a channel used by a reader in a passive tag system; and a control unit that, on the basis of the result of carrier sensing performed by the carrier sensing unit, issues an instruction to stand by for signal transmission.

Description

Technical Field

[0001] The present invention relates to technologies of a wireless communication device and a control method.

Background Art

[0002] Generally, IoT terminals use an unlicensed band and have a carrier sense function (see Non-Patent Document 1) in a transmission channel to prevent interference between terminals. And depending on the use case, there are times when it is necessary to prioritize the communication of the passive tag system while sharing the active wireless system and the passive tag system that was not conventionally assumed. FIGS. 9 and 10 are tables excerpting a part of the 920 MHz band channel allocation table. As shown in FIG. 10, for example, in the 920 MHz band, 92 blocks from 920.5 MHz to 923.5 MHz are the shared frequency bands of both systems, so interference will occur in this frequency band.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When it is necessary to share an active wireless system and a passive tag system in the same frequency band, when the mirror subcarrier method is used in the passive tag system, the response signal from the passive tag to the reader / writer is weak, so the case where the carrier sense of the IoT terminal of the active wireless system operates is rare.

[0005] Let's consider an example where a 920MHz band passive tag system uses a mirror subcarrier scheme, the passive tag system's reader / writer transmits a power supply signal to the passive tag on the power supply channel Ch.23 (center frequency 920.4MHz) (see Figure 9) of the 920MHz band channel allocation table, the passive tag transmits a response signal to the reader / writer on the data return channels Ch.24-28 (center frequencies 920.6, 920.8, 921.0, 921.2, 921.4MHz) (see Figure 10), and the IoT terminal of the active wireless system transmits signals on Ch.24-28.

[0006] In this example, as described above, the passive tag and the IoT device transmit signals using the same channel (Ch.24~28), so simultaneous transmission would cause interference. Here, the IoT device performs carrier sensing before transmitting a signal to confirm that there are no other wireless devices transmitting signals on the same channel nearby before transmitting the signal.

[0007] However, since communication between passive tags and reader / writers is generally assumed to be at a short distance of a few meters, the response signal from the passive tag to the reader / writer is weak, and the range in which an IoT terminal can carrier sense this response signal is very narrow, ranging from a few meters to tens of meters. IoT terminals that are tens of meters or more away cannot detect the response signal from the passive tag and therefore cannot transmit a signal.

[0008] If carrier sensing fails and the IoT device transmits a signal, as shown in Figure 8, this could interfere with the response signals of passive tags located within a few hundred meters or several kilometers of the IoT device, potentially disrupting their communication. In this case, communication with the passive tag system will be impossible until the IoT device's communication is complete.

[0009] In view of the above circumstances, the present invention aims to provide a technology that allows for the suitable sharing of active wireless systems and passive tag systems. [Means for solving the problem]

[0010] One aspect of the present invention is a wireless communication device comprising: a carrier sensing unit that performs carrier sensing on its own transmission channel before transmitting a signal, and also performs carrier sensing on the channel used by the reader of a passive tag system before transmitting a signal; and a control unit that instructs the device to wait for signal transmission based on the carrier sensing results performed by the carrier sensing unit.

[0011] One aspect of the present invention is a control method for a wireless communication device, comprising: a carrier sense step in which carrier sense is performed on the device's own transmission channel before transmitting a signal, and also on the channel used by the reader of a passive tag system before transmitting a signal; and a control step in which the device instructs the device to wait for signal transmission based on the carrier sense results obtained in the carrier sense step. [Effects of the Invention]

[0012] The present invention makes it possible to suitably share an active wireless system and a passive tag system. [Brief explanation of the drawing]

[0013] [Figure 1] This is a diagram of a wireless communication system. [Figure 2] This figure shows the frequency domain of each channel. [Figure 3] This figure shows examples of bandwidths that are subject to carrier sense. [Figure 4] This is a sequence diagram showing the processing flow when a power supply signal is detected. [Figure 5] This is a diagram to explain the design guidelines for career sense levels. [Figure 6] This figure shows an example of setting the career sense level. [Figure 7] This is a flowchart showing the processing flow of a wireless communication device. [Figure 8] This figure shows an example of interference between an active radio system and a passive tagging system. [Figure 9] A table excerpting a part of the 920 MHz band channel allocation table. [Figure 10] A table excerpting a part of the 920 MHz band channel allocation table.

Embodiments for Carrying Out the Invention

[0014] Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a wireless communication system 1. The wireless communication system 1 is composed of an active wireless system 10 and a passive tag system 20. The active wireless system 10 is composed of a wireless communication device 100 and a base station 300 according to the present embodiment. The passive tag system 20 is composed of a reader / writer 200 and a passive tag 400. In the present embodiment, a reader / writer is used, but instead of the reader / writer 200, a device having only a reader function may be used. Further, the wireless communication device 100 is, for example, an IoT (Internet Of Things) terminal or a communication device provided in an IoT terminal.

[0015] The wireless communication device 100 is composed of a carrier sense unit 111, a control unit 112, a transmission unit 120, and a transmission data storage unit 130. The carrier sense unit 111 includes a receiving function for receiving signals corresponding to each channel, such as a channel (hereinafter referred to as the "power supply channel") through which the reader / writer 200 transmits a power supply signal. Then, the carrier sense unit 111 performs carrier sense before signal transmission for its own transmission channel of the wireless communication device 100, and also performs carrier sense before signal transmission for the power supply channel used by the reader / writer 200 of the passive tag system 20. Note that the carrier sense unit 111 may perform carrier sense for a plurality of power supply channels in time division in order. Or, the carrier sense unit 111 may be equipped with a plurality of carrier sense units and perform carrier sense in parallel with them.

[0016] Based on the carrier sense result obtained by the carrier sense unit 111 (whether the signal of its own transmission channel or the power supply channel is detected), the control unit 112 instructs the transmission unit 120 to wait for signal transmission. Based on the carrier sense result obtained by the carrier sense unit 111 during signal transmission (whether the signal of the power supply channel is detected), the control unit 112 instructs to stop signal transmission.

[0017] Based on various instructions from the control unit 112, the transmission unit 120 transmits a signal to the base station 300, waits for signal transmission, or stops signal transmission. Specifically, when instructed to transmit by the control unit 112, the transmission unit 120 starts transmitting a signal to the base station 300. When instructed to stop signal transmission by the control unit 112, the transmission unit 120 stops transmitting a signal to the base station 300. When the transmission unit 120 is transmitting a signal to the base station 300 and is instructed to wait for signal transmission, it stops transmitting the signal, waits for a predetermined time, and then transmits the signal. The transmission data storage unit 130 stores the data carried on the signal transmitted by the transmission unit 120. The base station 300 includes a communication unit 310. The communication unit 310 receives the signal transmitted from the transmission unit 120. In the following description, the signal transmitted by the transmission unit 120 may be expressed as "its own signal".

[0018] The reader / writer 200 includes a transmission unit 210. The transmission unit 210 transmits a signal of the power supply channel to the passive tag 400, a signal instructing data reading / writing, and the like. The passive tag 400 is, for example, an RFID (Radio Frequency Identification) tag.

[0019] During communication between the reader / writer 200 and the passive tag 400, a narrowband power supply signal is continuously transmitted from the reader / writer 200 to the passive tag 400. Because the transmitting antenna of the wireless communication device 100 and the antenna for carrier sensing (hereinafter referred to as the "CS antenna") are close together, the self-signal is strongly received by the CS antenna. Therefore, by setting the carrier sense bandwidth to be narrow, the transmitted signal power within the carrier sense bandwidth can be reduced while the power supply signal power can be observed as usual. This allows for transmission stop operations depending on the presence or absence of the power supply signal without malfunctions caused by the self-signal. The carrier sense bandwidth should be set as narrow as possible while still being able to cover at least the transmission frequency deviation of the reader / writer 200.

[0020] Let's explain this using Figure 2. Figure 2 shows the spectrum 50 of the feed signal, the spectrum 60 of the self-signal, and the spectrum 70 of the tag response signal that the passive tag 400 transmits to the reader / writer 200. Regarding the spectrum 50 of the feed signal shown in Figure 2, for example, one channel in the 920 MHz band is 200 kHz wide, and the feed signal is in the narrow bandwidth of the 200 kHz width of Ch.23 with a center frequency of 920.4 MHz.

[0021] Furthermore, regarding the spectrum 60 of the self-signal, although the self-signal uses one channel with a width of 200 kHz, the spectrum actually extends beyond that 200 kHz width as shown in Figure 2 (the spectrum extends within the range that satisfies the requirements for adjacent channel leakage power and unwanted emission intensity as defined in ARIB STD-T108 version 1.4). Therefore, the spectrum 60 of the self-signal extends to the bandwidth of the feed signal channel, as shown in Figure 2.

[0022] If the power of the component that extends to the bandwidth of the power supply channel is calculated with a 200kHz bandwidth, the transmitted signal power will be greater than the power supply signal power. However, by narrowing the carrier sense bandwidth to match the narrow bandwidth of the power supply signal, the transmitted signal power will be less than the power supply signal power, thus preventing malfunctions caused by the transmitted signal.

[0023] Figure 3 shows examples of frequency bands targeted for carrier sensing. Figure 3 displays the channels (ch) and center frequencies for each standard (T106 (private radio station, land mobile station, 920MHz band mobile identification radio equipment), T107 (specified low-power radio station, 920MHz band mobile identification radio equipment)). Furthermore, Figure 3 shows the channels for private radio stations, land mobile stations (1W licensed stations), specified low-power radio stations (250mW), and data return channels.

[0024] For example, when the wireless communication device 100 transmits on Ch.14 (the "transmission channel" in the figure), the carrier sense unit 111 performs carrier sensing on Ch.11 and Ch.17 (the "CS target channels" in the figure). In this way, the carrier sense unit 111 performs carrier sensing on the power supply channels of the passive tag system on both sides of the transmission channel before transmitting its own signal and during the transmission of its own signal. It is also possible to configure the system to constantly perform carrier sensing on all power supply channels. However, in this case, the power consumption of the carrier sense unit 111 will increase. Furthermore, as described above, multiple power supply channels may be sequentially performed carrier sensing in a time-division multiplexer. Alternatively, the carrier sense unit 111 may be equipped with multiple carrier sense units that perform carrier sensing in parallel.

[0025] Figure 4 is a sequence diagram showing the processing flow when a power supply signal is detected by the carrier sense unit 111 while the self-signal is being transmitted. In Figure 4, the horizontal axis represents time. The signal transmitted by the reader / writer 200 and the signal transmitted by the passive tag 400 are also shown.

[0026] When reading data from the passive tag 400, a link establishment process is first performed between the reader / writer 200 and the passive tag 400. During the link establishment process and data reading process, the reader / writer 200 transmits a power supply signal. If the link is established through the link establishment process, the passive tag 400 begins reading the data. On the other hand, if the link is not established through the link establishment process, the link establishment process is performed again.

[0027] In Figure 4, when the carrier sense unit 111 detects a power supply signal at time Ta during self-signal transmission, the wireless communication device 100 starts the process of stopping self-signal transmission. As a result, the wireless communication device 100 stops self-signal transmission at time Tb. At this time, the self-signal transmission is stopped so that the time from time Ta to time Tb is, for example, within 1 ms. In this way, the impact on the passive tag system 20 can be minimized.

[0028] Furthermore, the passive tag 400 that responded to the link establishment process may be affected before the wireless communication device 100 completes its transmission stop. Generally, the reader / writer 200 periodically sends query commands to the passive tag 400 at intervals of several hundred microseconds. Therefore, the impact of interference on the passive tag 400 is limited to a delay of less than 1 ms in reading data from the passive tag 400.

[0029] Next, we will explain the guidelines for setting the carrier sense level to prevent interference. Figure 5 is a diagram illustrating the design guidelines for the carrier sense level. In Figure 5, region 80 indicates the detection range of the power supply signal. Region 90 indicates the interference range.

[0030] The carrier sense level of the carrier sense unit 111 is set to a range where the power supply signal detection range (area 80) is wider than the interference range (area 90) from the wireless communication device 100. If the carrier sense level is too high, malfunctions due to the self-signal are eliminated, but the detection range of the reader power supply signal becomes narrower. On the other hand, if the distance level is too low, the detection range of the power supply signal becomes wider, but malfunctions due to the self-signal occur, and the signal cannot be transmitted.

[0031] Therefore, the carrier sense level is set as shown in Figure 6, for example. Figure 6 is a diagram showing an example of setting the carrier sense level. The type of antenna used by the wireless communication device 100 to transmit its own signal can be a circularly polarized patch antenna or a dipole antenna. A dipole antenna can also be used as the antenna to receive the feed signal.

[0032] Figure 6 shows the carrier sense level for each antenna type, the station type of the reader / writer 200, the feed signal detection range, and the interference range. As shown in Figure 6, when the wireless communication device 100 transmits with a circularly polarized patch antenna, the carrier sense level is set to -59 dBm. In this case, the feed signal detection range for the reader / writer 200 of a 1W station is 1360 m, while the interference range is 1460 m.

[0033] Furthermore, when the wireless communication device 100 transmits using a dipole antenna, setting the carrier sense level to -66 dBm results in a feed signal detection range of 3260 m compared to the interference range of 2900 m for the 1W station's reader / writer 200.

[0034] Next, the processing flow of the wireless communication device 100 will be explained. Figure 7 is a flowchart showing the processing flow of the wireless communication device 100. The wireless communication device 100 prepares to transmit before transmitting its own signal (step S101). At this time, the control unit 112 determines whether or not a signal for the transmission channel or power supply channel of its own signal has been detected by the carrier sense unit 111 (step S102). If a signal is detected (step S102: YES), the control unit 112 instructs the transmission unit 120 to wait for a predetermined time before transmitting its own signal (step S107), and returns to step S102.

[0035] If no signal is detected in step S102 (step S102: NO), the control unit 112 instructs the transmitter 120 to start transmitting its own signal (step S103). Subsequently, the control unit 112 determines whether or not a signal on the power supply channel has been detected by the carrier sense unit 111 (step S104). If a signal is detected (step S104: YES), the control unit 112 instructs the transmitter 120 to stop transmitting its own signal and to wait for a predetermined time (step S105), and returns to step S102.

[0036] If no signal is detected in step S104 (step S104: YES), the control unit 112 determines whether or not the transmission of its own signal has been completed (step S106). If the transmission of its own signal has not been completed (step S106: NO), the process returns to step S104. If the transmission of its own signal has been completed (step S106: YES), this process ends.

[0037] As explained above, in this embodiment, carrier sensing is performed not only before the transmission of the self-signal but also during transmission. By doing so, even during the transmission of the self-signal, if a power supply signal is detected, the transmission of the self-signal can be stopped, thereby minimizing the impact on the passive tag system 20. Therefore, according to this embodiment, the active wireless system and the passive tag system can be suitably shared.

[0038] The control unit 112 may be configured using a processor such as a CPU (Central Processing Unit) and memory. In this case, the control unit 112 functions when the processor executes a program. Note that all or part of the functions of the control unit 112 may be implemented using hardware such as an ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), or FPGA (Field Programmable Gate Array). The above program may be recorded on a computer-readable recording medium. Computer-readable recording media include, for example, portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and semiconductor storage devices (e.g., SSDs: Solid State Drives), as well as storage devices such as hard disks and semiconductor storage devices built into computer systems. The above program may be transmitted via a telecommunications line.

[0039] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention. [Industrial applicability]

[0040] The present invention is applicable to systems that share the same frequency as an active wireless system and a passive tag system. [Explanation of Symbols]

[0041] 1... Wireless communication system, 10... Active wireless system, 20... Passive tag system, 100... Wireless communication device, 111... Carrier sense unit, 112... Control unit, 120... Transmitter unit, 130... Transmit data storage unit, 200... Reader / writer, 210... Transmitter unit, 300... Base station, 310... Communication unit, 400... Passive tag

Claims

1. A carrier sensing unit performs a first carrier sensing before transmitting a transmission signal using its own transmission channel, and also performs a second carrier sensing before transmitting the transmission signal for the power supply channel used by the passive tag system's reader. A control unit that instructs the transmission signal to wait for transmission based on the carrier sensing results of the first and second carrier sensing performed by the carrier sensing unit, A wireless communication device.

2. The carrier sensing unit performs a third carrier sensing on the power supply channel used by the leader, even while the transmission of the transmission signal is in progress. The wireless communication device according to claim 1, wherein the control unit instructs the stop of transmitting the transmission signal based on the carrier sense result of the third carrier sense performed by the carrier sense unit during the transmission of the transmission signal.

3. The wireless communication device according to claim 2, wherein the carrier sense unit sets the carrier sense bandwidth for performing the second and third carrier sense of the power supply channel used by the reader to a range that can at least cover the transmission frequency deviation of the reader.

4. The wireless communication device according to claim 2, characterized in that the carrier sense unit sets the carrier sense level in a range where the area of ​​the power supply signal detection range is wider than the interference range caused by the transmission signal it transmits itself.

5. The wireless communication device according to claim 2, wherein the carrier sensing unit sequentially performs the second and third carrier sensing on a plurality of power supply channels used by the reader in a time-division manner.

6. The wireless communication device according to claim 2, wherein the carrier sensing unit performs the second and third carrier sensing in parallel on a plurality of power supply channels used by the reader.

7. A method for controlling a wireless communication device, A carrier sense step in which a first carrier sense is performed before transmitting a transmission signal using its own transmission channel, and a second carrier sense is performed before transmitting the transmission signal for the power supply channel used by the passive tag system's leader, A control step which instructs the system to wait for the transmission of the transmission signal based on the carrier sense results of the first and second carrier senses performed in the carrier sense step, A control method that includes [a specific feature / method].

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