Spatial sensing method, control device, and program

Abstract

Provided is a spatial sensing method in a communication system including a transmission device and a reception device, wherein the transmission device transmits at least two OAM mode signals of different frequencies simultaneously, and on the basis of the fluctuation of the received power of the signals measured by the reception device, detects an obstacle in a space between the transmission device and the reception device.

Description

[Technical Field]

[0001] The present invention relates to a technique for spatially multiplexing and transmitting wireless signals using the orbital angular momentum (OAM) of electromagnetic waves. [Background technology]

[0002] In recent years, spatial multiplexing transmission technology for wireless signals using OAM has been studied to improve transmission capacity (for example, Non-Patent Document 1). Electromagnetic waves with OAM have equiphase planes distributed in a spiral pattern along the propagation direction, centered on the propagation axis. Electromagnetic waves with different OAM modes propagating in the same direction have orthogonal spatial phase distributions in the direction of the rotation axis. Therefore, signals can be multiplexed and transmitted by separating the signals of each OAM mode modulated with different signal sequences at the receiving device.

[0003] In a wireless communication system using this OAM multiplexing technology, a uniform circular array antenna (hereinafter referred to as a UCA (Uniform Circular Array)) in which multiple antenna elements are arranged at equal intervals in a circle is used to generate, combine, and transmit multiple OAM modes, thereby achieving spatially multiplexed transmission of different signal sequences (see, for example, Non-Patent Document 2). A Butler circuit (Butler matrix circuit), for example, is used to generate and separate signals for multiple OAM modes. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] J.Wang et al., "Terabit free-space data transmission employing orbital angular momentum multiplexing," Nature Photonics, Vol.6, pp.488-496, July 2012. [Non-patent document 2] Y.Yan et al., "High-capacity millimeter-wave communications with orbital angular momentum multiplexing," Nature Commun., vol.5, p.4876, Sep. 2014. Summary of the Invention [Problem to be solved by the invention]

[0005] When an obstacle intrudes into a space where line-of-sight (LoS) communication is being performed, it may be necessary to decide on countermeasures such as switching networks. However, in conventional technologies for such applications, the presence or absence of an obstacle is determined from the communication results (deterioration in quality), which can result in a significant delay in intrusion detection.

[0006] Furthermore, when detecting objects using radar, LiDAR, etc., it is necessary to install a large number of dedicated sensors or to equip distributed IoT devices with many sensing functions, which is undesirable from the standpoint of cost and power consumption.

[0007] The present invention has been made in view of the above points, and an object of the present invention is to provide a technique for performing obstacle detection at high speed with a simple device configuration. [Means for solving the problem]

[0008] According to the disclosed technology, there is provided a spatial sensing method in a communication system including a transmitting device and a receiving device, comprising: the transmitting device simultaneously transmits signals in at least two OAM modes at different frequencies; Detecting an obstacle in a space between the transmitting device and the receiving device based on fluctuations in the received power of the signal measured by the receiving device. A spatial sensing method is provided. [Effects of the Invention]

[0009] The disclosed technology provides a technology for performing obstacle detection at high speed with a simple device configuration. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 10 is a diagram illustrating an example of phase setting of a UCA for generating an OAM mode signal. [Figure 2] 1A and 1B are diagrams illustrating examples of phase distribution and signal intensity distribution of an OAM multiplexed signal. [Figure 3] 1 is a configuration diagram of a communication system according to an embodiment of the present invention; [Figure 4] 1 is a flowchart illustrating an example of a processing flow according to an embodiment of the present invention. [Figure 5] FIG. 10 is a diagram for explaining the intensity distribution of an OAM mode signal. [Figure 6] FIG. 10 is a diagram for explaining the intensity distribution of an OAM mode signal. [Figure 7] FIG. 10 is a diagram for explaining obstacle detection. [Figure 8] FIG. 10 is a diagram for explaining estimation of atmospheric attenuation. [Figure 9] FIG. 2 is a configuration diagram of a control device. [Figure 10] FIG. 1 is a diagram illustrating the configuration of a computer. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention (the present embodiment) will be described with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0012] (About UCA) First, a basic setting and operation example of the UCA used in the transmitting device and receiving device of this embodiment will be described. As will be described later, if the purpose is only to detect obstacle intrusion, there is no need to provide the UCA in the receiving device.

[0013] Fig. 1 is a diagram showing an example of phase settings of a UCA for generating an OAM mode signal. The UCA shown in Fig. 1 is a UCA consisting of eight antenna elements.

[0014] In Figure 1, signals for OAM modes 0, 1, 2, 3, ... on the transmitting side are generated by the phase difference of the signals supplied to each antenna element (indicated by ●) of the UCA. That is, signals for OAM mode n are generated by setting the phase of the signal supplied to each antenna element so that the phase rotates n times (n x 360 degrees). For example, when the UCA is configured with m = 8 antenna elements as shown in Figure 1 and a signal for OAM mode n = 2 is generated, a phase difference of 360n / m = 90 degrees counterclockwise is set for each antenna element (0 degrees, 90 degrees, 180 degrees, 270 degrees, 0 degrees, 90 degrees, 180 degrees, 270 degrees) so that the phase rotates twice, as shown in Figure 1 (3).

[0015] Note that a signal with the phase rotation direction reversed to that of an OAM mode n signal is called OAM mode -n. For example, the phase rotation direction of a positive OAM mode signal is counterclockwise, and the phase rotation direction of a negative OAM mode signal is clockwise.

[0016] Spatial multiplexing wireless communication can be performed by generating different signal sequences as signals in different OAM modes and transmitting the generated signals simultaneously. On the transmitting side, signals to be transmitted in each OAM mode can be generated and combined in advance and the combined signal for each OAM mode can be transmitted using a single UCA, or multiple UCAs can be used to transmit signals for each OAM mode using different UCAs for each OAM mode.

[0017] To separate the OAM multiplexed signal on the receiving side, the phase of each antenna element of the UCA on the receiving side can be set to be opposite to the phase of the antenna element on the transmitting side.

[0018] However, if interference occurs between OAM modes due to factors such as misalignment between the transmitting and receiving antennas, it becomes necessary to separate the mixed OAM mode signals through digital signal processing such as channel equalization and successive interference cancellation. Interference between OAM modes means, for example, that a signal transmitted from a transmitting device in OAM mode 1 is output as an OAM mode 2 signal on the receiving side.

[0019] Figure 2 shows examples of the phase distribution and signal intensity distribution of an OAM multiplexed signal. In Figures 2(1) and (2), the arrows represent the phase distribution of OAM mode 1 and OAM mode 2 signals as seen from the transmitter at an end face perpendicular to the propagation direction (orthogonal propagation plane). The arrows start at 0 degrees, and the phase changes linearly until they end at 360 degrees. In other words, an OAM mode n signal propagates with its phase rotating n times (n x 360 degrees) on the orthogonal propagation plane. Note that the arrows for the phase distribution of OAM mode -1 and -2 signals point in opposite directions.

[0020] The signal intensity distribution and the position where the signal intensity is maximized differ for each OAM mode. However, the intensity distribution is the same for the same OAM mode but with a different sign. Specifically, the higher the order of the OAM mode, the farther the position where the signal intensity is maximized is from the propagation axis (Non-Patent Document 2). Here, an OAM mode with a larger value is referred to as a higher-order mode. For example, an OAM mode 3 signal is a higher-order mode than OAM mode 0, OAM mode 1, and OAM mode 2 signals.

[0021] Figure 2(3) shows the position where the signal strength is maximum for each OAM mode as a circle. The higher the OAM mode, the farther the position where the signal strength is maximum is from the central axis. Also, the beam diameter of the OAM mode multiplexed signal expands depending on the propagation distance, and the circle showing the position where the signal strength is maximum for each OAM mode becomes larger.

[0022] (Outline of the embodiment) In this embodiment, spatial sensing is performed using OAM. Specifically, a transmitting device 100 simultaneously transmits signals in multiple OAM modes with different frequencies, and a receiving device 200 observes the received waveforms or received power, thereby detecting with high accuracy that an obstacle has entered the transmission path between the transmitting device 100 and the receiving device 200 with a simple device configuration.

[0023] That is, the receiving device 200 can detect with high accuracy that an obstacle has entered the space between the transmitting device 100 and the receiving device 200. The space between the transmitting device 100 and the receiving device 200 is a space through which signals of multiple OAM modes, which are transmitted by the transmitting device 100 and received by the receiving device 200, propagate.

[0024] This embodiment utilizes the property that the power distribution of multiple OAM mode signals transmitted from transmitting device 100, which differ in frequency by Δf, rotates around the propagation axis with a period of Δf. Due to this property, when an obstacle that blocks electromagnetic waves enters, the received power oscillates with Δf, and therefore the entrance of the obstacle can be detected with high accuracy by detecting the frequency of Δf.

[0025] The system configuration and operation example of this embodiment will be described in detail below.

[0026] (Example of a communication system configuration) 3 is a diagram showing an example of the configuration of a communication system according to an embodiment of the present invention. This communication system includes a transmitting device 100 and a receiving device 00.

[0027] 3, the transmitting device 100 includes a waveform generation processing unit 110, an OAM generation processing unit 120, an antenna unit 130, and a communication signal processing unit 140. The receiving device 200 includes an antenna unit 210, an OAM separation processing unit 220, a measurement unit 230, a detection unit 240, a control unit 250, a communication signal processing unit 260, and an entrance direction estimation unit 270.

[0028] Note that the receiving device 200 shown in FIG. 3 is configured to perform communication using signals in the OAM mode as well as detect the intrusion of obstacles. If only the detection of obstacle intrusion is the purpose, the OAM separation processing unit 220 may not be provided.

[0029] Both the antenna units 130 and 210 have a UCA. Also, in the present embodiment, both the OAM generation processing unit 120 and the OAM separation processing unit 220 are analog circuits such as Butler matrices. Further, as an analog circuit (analog element) for OAM generation / separation, a spiral phase plate obtained by processing the thickness of a dielectric in a spiral shape may be used.

[0030] However, using an analog circuit for OAM generation / separation is just an example, and OAM generation / separation may be performed by digital processing.

[0031] (Operation example) Hereinafter, an operation example of the communication system will be described according to the procedure of the flowchart in FIG. 4.

[0032] <S101: Transmission of signals in the OAM mode> In S101, the transmission device 100 transmits signals in a plurality of OAM modes. Specifically, it is as follows.

[0033] The waveform generation processing unit 110 generates carrier waves of a plurality of different frequencies. The communication signal processing unit 140 generates an analog signal from the transmission signal sequence (digital signal). The OAM generation processing unit 120 generates signals in a plurality of OAM modes from the analog signal carried on the carrier wave. The antenna unit 130 simultaneously transmits the generated signals in a plurality of OAM modes at different frequencies.

[0034] As an example, the antenna unit 130 transmits the signal of OAM mode 1 at the frequency f [Hz] and the signal of OAM mode 2 at the frequency f + Δf [Hz]. The properties of the OAM multiplex signal transmitted in this way will be described with reference to FIG. 5.

[0035] For comparison, the upper part of Fig. 5 shows the intensity distribution of radio waves when antenna unit 130 transmits an OAM mode 1 signal at frequency f [Hz] and also transmits an OAM mode 2 signal at the same frequency f [Hz]. This intensity distribution corresponds to the power distribution of received signals on a flat plate placed perpendicular to the propagation axis between transmitting device 100 and receiving device 200. The same is true for the lower part of Fig. 5. The origin of the x-y coordinates shown in the upper and lower parts of Fig. 5 corresponds to the propagation axis.

[0036] As shown in the upper part of Figure 5, when OAM mode 1 signals and OAM mode 2 signals are transmitted simultaneously at the same frequency, the intensity of one area located at a position shifted from the origin becomes greater than the intensity of other areas. We will call this area the "specific area." In the example of Figure 5, the shape of the specific area is circular, but it is not limited to circular shapes. When OAM mode 1 signals and OAM mode 2 signals are transmitted simultaneously at the same frequency, the specific area does not move and its position remains fixed.

[0037] On the other hand, when an OAM mode 1 signal is transmitted at a frequency f [Hz] and an OAM mode 2 signal is simultaneously transmitted at a frequency f + Δf [Hz], the specific area rotates around the origin at a frequency Δf, as shown in the lower part of Fig. 5. In this embodiment, the size of the specific area and the distance from the propagation axis of the specific area are assumed to be suitable for detecting obstacles (people, animals, vehicles, drones, etc.).

[0038] The phenomenon shown in FIG. 5 is not limited to OAM mode 1 and OAM mode 2, but is a phenomenon that occurs for two OAM mode signals with an OAM mode order difference of only one.

[0039] Furthermore, for two OAM mode signals whose OAM mode orders differ by two, two specific regions are generated, as shown in Fig. 6. Furthermore, as in the case of Fig. 5, if the frequency difference between the two OAM mode signals is Δf, the two specific regions shown in Fig. 6 rotate with the frequency Δf.

[0040] Similarly, for signals of two OAM modes with a difference of N (N is an integer greater than or equal to 1) in the order of the OAM mode, N specific regions occur. If the frequency difference between the signals of the two OAM modes is Δf, the N specific regions rotate at the frequency Δf.

[0041] Also, the number of multiple OAM modes transmitted at different frequencies, that is, the number of multiple OAM modes used for obstacle detection is not limited to 2, and may be 3 or more.

[0042] Here, as an example, the following description will be given assuming that signals of two OAM modes with a frequency difference of Δf are transmitted.

[0043] <S102: OAM multiplexed signal reception, received power measurement> The antenna unit 210 of the receiving device 200 receives the OAM multiplexed signal. The OAM separation processing unit 220 separates the signals of each OAM mode from the OAM multiplexed signal. The communication signal processing unit 250 generates and outputs a received signal sequence from the signals of each OAM mode obtained by the OAM separation processing unit 220.

[0044] The measurement unit 230 measures (detects) the total received power of the signals of each OAM mode. As described above, if it is for detecting the intrusion of an obstacle, the OAM separation processing unit 230 is not necessary. When the OAM separation processing unit 230 is not provided, the measurement unit 230 measures the received power of the OAM multiplexed signal received by the antenna unit 210. Also, even when the OAM separation processing unit​​​​​​​<S103: Δf Detection> The detection unit 240 detects the frequency component of Δf from the fluctuation of the received power measured by the measurement unit 230 (which may be called "undulation").

[0047] <S104, S105: Judgment> The detection unit 240 compares the magnitude (P) of the frequency component of Δf of the received power with a predetermined threshold value (S104), and when the magnitude (P) of the frequency component of Δf exceeds the threshold value, it determines that there is an intrusion of an obstacle (S105). Note that P, which is the object of comparison with the threshold value, may be the following (1) or (2). Both of the following (1) and (2) are included in the above-mentioned "magnitude of the frequency component of Δf".

[0048] (1) Among the received powers that fluctuate with the period of Δf, let P be the difference obtained by subtracting the received power at the part where the received power is the lowest from the received power at the part where the received power is the highest.

[0049] [[ID=1 ]](2) Among the received powers that fluctuate with the period of Δf, let P be the ratio obtained by dividing the received power at the part where the received power is the highest by the received power at the part where the received power is the lowest.

[0050] A specific example will be described with reference to FIG. 7. FIG. 7 shows an example in which a signal in OAM mode 1 is transmitted at a frequency f [Hz] and a signal in OAM mode 2 is transmitted at a frequency f + Δf [Hz].

[0051] The upper part of FIG. 7 shows the same power distribution as the lower part of FIG. 5. As shown in the upper part of FIG. 7, it is assumed that an obstacle A has invaded the space between the transmitting device 100 and the receiving device 200. As shown in the upper part of FIG. 7, the obstacle A exists at a position where a specific area partially overlaps by rotating the specific area around the origin. That is, by rotating the specific area around the origin, the radio wave of the specific area is periodically blocked (that is, at a frequency Δf) by the obstacle A. [[ID=]]

[0052] As a result, the detection unit 240 detects the power fluctuation with a frequency of Δf shown in the lower part of FIG. 7. Thereby, it can be determined that there is an obstacle A.

[0053] Note that, as shown in FIG. 8, when there is no clear obstacle between the transmission device 100 and the reception device 200 but there is rainfall, fog, smoke, etc., the detection unit 240 detects a uniform decrease in power without detecting periodic fluctuations in power.

[0054] For example, the detection unit 240 usually detects a constant value P as the magnitude of power. However, when it detects that the power has become "P - LP", it determines that there is an atmospheric attenuation amount LA corresponding to the power decrease amount LP. Regarding the relationship between the power decrease amount LP and the atmospheric attenuation amount LA, it may be held in a table or the like in advance, or an approximate formula representing the relationship between the power decrease amount LP and the atmospheric attenuation amount LA may be created, and the atmospheric attenuation amount LA may be calculated from the power decrease amount LP using the approximate formula. <000​​​​​​​​​​​​​​​

[0058] For example, if the control signal is a signal for controlling communication in the communication system shown in Fig. 3, the control signal is notified to communication signal processing unit 140 of transmitting device 100 as shown in Fig. 3. As an example, the control signal performs control such as switching communication by the communication system shown in Fig. 3 to another communication system.

[0059] Furthermore, the control unit 250 may notify the person (or a terminal held by the person) of information indicating that an intrusion has occurred. Furthermore, the control unit 250 may notify the person (or a terminal held by the person) of information indicating that an intrusion has occurred and the direction of the intrusion. Such notification information is also considered to be included in the "control signal."

[0060] (Other configurations) The detection unit 240 and the control unit 250 may be provided outside the receiving device 200. A device provided outside the receiving device 200 and including the detection unit 240 and the control unit 250 may be called a control device. Furthermore, the entire device including the detection unit 240 and the control unit 250 may be called a control device. In other words, the receiving device 200 may be called a control device. When the control device is provided outside the receiving device 200, the control device and the receiving device 200 are connected via a network.

[0061] Fig. 9 shows an example of the configuration of a control device. The control device shown in Fig. 9 includes a detection unit 240, a control unit 250, and an intrusion direction estimation unit 270. The operation of each functional unit is as described above. When the control device and the receiving device 200 are connected via a network, the received power measured by the receiving device 200 is transmitted to the control device via the network. Note that the control device may not include the intrusion direction estimation unit 270.

[0062] The control device can be realized by, for example, a computer and software. That is, the control device can be realized by executing a program corresponding to the processing performed by the control device using hardware resources such as a CPU and memory built into the computer. The program can be recorded on a computer-readable recording medium (such as a portable memory) and stored or distributed. The program can also be provided via a network such as the Internet or email. The computer can also be a virtual machine on a cloud.

[0063] Fig. 10 is a diagram showing an example of the hardware configuration of the computer. The computer in Fig. 10 includes a drive device 1000, an auxiliary storage device 1002, a memory device 1003, a CPU 1004, an interface device 1005, a display device 1006, an input device 1007, an output device 1008, and the like, all of which are interconnected by a bus BS. The computer may further include a GPU.

[0064] A program for realizing processing on the computer is provided by a recording medium 1001 such as a CD-ROM or a memory card. When the recording medium 1001 storing the program is set in the drive device 1000, the program is installed from the recording medium 1001 to the auxiliary storage device 1002 via the drive device 1000. However, the program does not necessarily have to be installed from the recording medium 1001, but may be downloaded from another computer via a network. The auxiliary storage device 1002 stores the installed program as well as necessary files, data, etc.

[0065] The memory device 1003 reads and stores the program from the auxiliary storage device 1002 when an instruction to start the program is received. The CPU 1004 realizes the functions related to the control device in accordance with the program stored in the memory device 1003. The interface device 1005 is used as an interface for connecting to a network, etc. The display device 1006 displays a GUI (Graphical User Interface) or the like according to the program. The input device 1007 is composed of a keyboard, mouse, buttons, a touch panel, etc., and is used to input various operation instructions. The output device 1008 outputs the results of calculations.

[0066] (Effects of the embodiment) According to the technology of the present embodiment, it is possible to realize spatial sensing that performs high-speed obstacle detection with a simple device configuration.

[0067] That is, in this embodiment, a sensor such as LiDAR is not required as a detection means on the receiving side, and only a power detection means is required. Also, the OAM on the transmitting side can be generated using analog elements (e.g., Butler Matrix, Spiral Phase Plate, etc.). This simplifies the device configuration and reduces the digital signal processing load. Furthermore, a simple method based on power fluctuations is used to determine whether an obstacle is intruding, enabling high-speed, highly accurate obstacle detection.

[0068] Another advantage is that obstacle detection can be performed simultaneously while performing large-capacity spatial multiplexing transmission using OAM over radio waves in the THz band, etc. The technology according to the present embodiment can be used, for example, to identify the intrusion and intrusion direction of a person or vehicle passing through a gate, but the applications are not limited to this.

[0069] (Addendum) This specification describes at least the spatial sensing method, control device, and program described in the following sections. (Additional note 1) A spatial sensing method in a communication system including a transmitting device and a receiving device, the transmitting device simultaneously transmits signals in at least two OAM modes at different frequencies; Detecting an obstacle in a space between the transmitting device and the receiving device based on fluctuations in the received power of the signal measured by the receiving device. Spatial sensing methods. (Additional note 2) A frequency component corresponding to the difference in frequency of the two OAM mode signals is detected from the fluctuations in the received power, and if the magnitude of the frequency component exceeds a threshold, it is determined that the obstacle is present. Item 1. A spatial sensing method according to item 1. (Additional note 3) The direction of the obstacle is detected based on the phase of the fluctuation of the received power. 3. The spatial sensing method according to claim 1 or 2. (Additional note 4) The transmission device uses analog elements for generating the OAM mode. A spatial sensing method according to any one of appendixes 1 to 3. (Additional note 5) A control device that performs spatial sensing in a communication system including a transmitting device that simultaneously transmits at least two OAM mode signals of different frequencies and a receiving device, a detection unit that detects an obstacle in a space between the transmitting device and the receiving device based on fluctuations in the received power of the signal measured by the receiving device; a control unit that outputs a control signal in response to the detection of the obstacle; A control device comprising: (Additional note 6) A program for causing a computer to function as each part of the control device described in appended paragraph 5.

[0070] Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0071] 100 Transmitting device 110 Waveform generation processing section 120 OAM generation processing unit 130 Antenna section 140 Communication signal processing section 200 receiving device 210 Antenna section 220 OAM separation processing unit 230 Measuring section 240 Detector 250 control section 260 Communication signal processing section 270 Intrusion direction estimation unit 1000 Drive Device 1001 Recording media 1002 Auxiliary storage 1003 Memory device 1004 CPU 1005 Interface device 1006 Display device 1007 Input Device 1008 Output Device

Claims

1. A spatial sensing method in a communication system including a transmitting device and a receiving device, The transmitting device simultaneously transmits at least two OAM mode signals at different frequencies; Detecting an obstacle in a space between the transmitting device and the receiving device based on fluctuations in the received power of the signal measured by the receiving device. Spatial sensing methods.

2. The at least two OAM modes are two OAM modes, and a frequency component that is the difference in frequency between the signals of the two OAM modes is detected as a frequency component of the fluctuation in the received power, and if the magnitude of the frequency component exceeds a threshold, it is determined that the obstacle is present. The spatial sensing method according to claim 1 .

3. The direction of the obstacle is detected based on the phase of the fluctuation of the received power. The spatial sensing method according to claim 1 or 2.

4. The transmission device uses analog elements for generating the OAM mode. The spatial sensing method according to claim 1 or 2.

5. A control device that performs spatial sensing in a communication system including a transmitting device that simultaneously transmits at least two OAM mode signals of different frequencies and a receiving device, a detection unit that detects an obstacle in a space between the transmitting device and the receiving device based on fluctuations in the received power of the signal measured by the receiving device; a control unit that outputs a control signal in response to the detection of the obstacle; A control device comprising:

6. A program for causing a computer to function as each unit in the control device according to claim 5.

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