Path kind discrimination device, positioning system, path kind discrimination method, and computer program

Abstract

To improve the positioning precision of a terminal of a radio system.SOLUTION: There is provided a path kind discrimination device that determines which of a direct path through which a radio signal reaches a terminal directly from a base station and a cascade path through which the radio signal reaches the terminal from the base station through a reflection plate a propagation path through which the radio signal transmitted from the base station reaches the terminal is, and the path kind discrimination device discriminates which of the direct path and the cascade path the propagation path is based upon a result of comparison between ranking of levels of incident electric power of respective beams of the base station to the reflection plate and ranking of levels of received electric power of respective beams of the base station at the terminal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a path type discrimination device, a positioning system, a path type discrimination method, and a computer program. [Background technology]

[0002] Conventionally, a technology that uses an intelligent reflecting surface (IRS), a reflector whose reflection direction can be arbitrarily controlled, has been considered as a countermeasure against blind zones in high-frequency bands in wireless systems. With this technology, the reflection pattern of the IRS is directed toward a user terminal located in the blind zone, allowing the wireless signal transmitted from the base station to reach the user terminal via the IRS, and establishing communication between the user terminal and the base station.

[0003] Also, a method of positioning a user terminal in a wireless environment where an IRS is installed is being studied. One of the common positioning methods is a TOA (Time of Arrival) positioning method using the TOA between a transmitting point and a receiving point (see, for example, Non-Patent Document 1). In the TOA positioning method described in Non-Patent Document 1, in a wireless environment where the propagation path of a wireless signal between a user terminal located in a blind zone and a base station is a path (direct path) that directly reaches the user terminal from the base station and the base station and only a path (cascade path) via the IRS is cut off, the distance from the IRS to the user terminal is calculated by subtracting the known distance between the base station and the IRS from the distance between the base station and the user terminal calculated from the TOA between the base station and the user terminal. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] A. Albanese, P. Mursia, V. Sciancalepore, and X. Costa-Perez, “PAPIR: Practical RIS-aided Localization via Statistical User Information,” in 2021 IEEE 22nd International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 2021, pp. 531-535. Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the TOA positioning method described in Non-Patent Document 1 mentioned above, when the user terminal is located within the line of sight (LOS) of the base station, the positioning accuracy deteriorates.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to improve the positioning accuracy of a terminal in a wireless system. [Means for solving the problem]

[0007] One aspect of the present invention is a path type discrimination device that determines whether a propagation path through which a radio signal transmitted from a base station reaches a terminal is a direct path that reaches the terminal directly from the base station, or a cascade path that reaches the terminal from the base station via a reflector, and determines whether the propagation path is the direct path or the cascade path based on the result of a comparison between a ranking of the magnitude of incident power of each beam of the base station to the reflector and a ranking of the magnitude of received power of each beam of the base station at the terminal. One aspect of the present invention is a path type discrimination device that, in the above-mentioned path type discrimination device, determines that the propagation path is the direct path if the distance between the base station and the terminal, calculated from the TOA (Time of Arrival) between the base station and the terminal, is less than the distance between the base station and the reflector. One aspect of the present invention is a path type discrimination device, in which, in the above-mentioned path type discrimination device, if the comparison result is a match, the propagation path is discriminated to be the cascade path, and if the comparison result is a mismatch, the propagation path is discriminated to be the direct path. One aspect of the present invention is a path type discrimination device that, in the above-mentioned path type discrimination device, when a change in the received power is found as a result of comparing the received power before and after changing the state of the reflector, discriminates that the propagation path is the cascade path.

[0008] One aspect of the present invention is a positioning system that measures the position of a terminal that receives multiple radio signals transmitted from multiple base stations using a TOA (Time of Arrival) positioning method, and is equipped with any of the path type discrimination devices described above, and determines whether the TOA between the base station and the terminal is to be used as the TOA of a direct path or as the TOA of a cascade path based on the discrimination result of the path type discrimination device.

[0009] One aspect of the present invention is a path type discrimination method for determining whether a propagation path of a radio signal transmitted from a base station to a terminal is a direct path that reaches the terminal directly from the base station, or a cascade path that reaches the terminal from the base station via a reflector, in which a path type discrimination device determines whether the propagation path is the direct path or the cascade path based on a comparison result between a ranking of the magnitude of incident power of each beam of the base station to the reflector and a ranking of the magnitude of received power of each beam of the base station at the terminal.

[0010] One aspect of the present invention is a computer program that causes a computer to execute a path type discrimination step of discriminating whether a propagation path for a radio signal transmitted from a base station to reach a terminal is a direct path that reaches the terminal directly from the base station, or a cascade path that reaches the terminal from the base station via a reflector, and the path type discrimination step discriminates whether the propagation path is the direct path or the cascade path based on a comparison result between a ranking of the magnitude of incident power of each beam of the base station to the reflector and a ranking of the magnitude of received power of each beam of the base station at the terminal. Effect of the Invention

[0011] According to the present invention, it is possible to obtain an effect of improving the positioning accuracy of a terminal in a wireless system. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram showing an example of the configuration of a positioning system according to an embodiment; [Diagram 2] FIG. 1 is a diagram for explaining a wireless environment according to an embodiment. [Diagram 3] FIG. 1 is a diagram for explaining a wireless environment according to an embodiment. [Figure 4] FIG. 11 is a diagram for explaining a path type determination method according to an embodiment. [Diagram 5] FIG. 11 is a diagram for explaining a path type determination method according to an embodiment. [Figure 6] FIG. 11 is a diagram for explaining a path type determination method according to an embodiment. [Figure 7] FIG. 11 is a diagram for explaining a path type determination method according to an embodiment. [Figure 8] FIG. 2 is a diagram for explaining a position estimation method according to an embodiment. [Figure 9] FIG. 2 is a diagram for explaining a position estimation method according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 is a block diagram showing an example of the configuration of a positioning system according to an embodiment. In FIG. 1, the positioning system 1 includes a path type determination unit 11, an environment setting unit 12, an information acquisition unit 13, and a position estimation unit .

[0014] Each function of the positioning system 1 is realized by the positioning system 1 including computer hardware such as a CPU (Central Processing Unit) and a memory, and the CPU executing a computer program stored in the memory. The positioning system 1 may be configured using a general-purpose computer device, or may be configured as a dedicated hardware device. For example, the positioning system 1 may be configured using a server computer connected to a communication network such as the Internet. Each function of the positioning system 1 may be realized by cloud computing. The positioning system 1 may be realized by a single computer, or may be realized by distributing the functions of the positioning system 1 among multiple computers. The positioning system 1 may be configured to open a website using, for example, a WWW system.

[0015] The path type discrimination unit 11 discriminates whether the propagation path of the radio signal transmitted from the base station to the terminal is a direct path or a cascade path. A direct path is a propagation path that directly reaches the terminal from the base station. A cascade path is a propagation path that reaches the terminal from the base station via a reflector. In this embodiment, an IRS is used as an example of a reflector.

[0016] 2 and 3 are diagrams for explaining the wireless environment according to this embodiment. In FIG. 2, the direct path from the base station (BS) is blocked by a shield such as a building. For this reason, a user terminal in a shielded area cannot receive a wireless signal from the base station via the direct path. On the other hand, a user terminal in a shielded area can receive a wireless signal from the base station via a cascade path from the base station via an IRS.

[0017] As shown in Fig. 3(1), the cascade path is a propagation path that goes from the base station to the user equipment (UE) via the IRS. As shown in Fig. 3(2), the direct path is a propagation path that goes directly from the base station to the user equipment.

[0018] Here, the path type determination method according to the present embodiment will be described with reference to Figures 4 to 7. Figures 4 to 7 are diagrams for explaining the path type determination method according to the present embodiment.

[0019] Figures 4 and 5 show the results of sorting the beam identifiers (beam IDs (BIDs)) of base stations in order of the magnitude of the incident power of the radio signal transmitted from the base station to the IRS, and the results of sorting the BIDs in order of the magnitude of the received power (UE received power) of the radio signal transmitted from the base station at the user terminal.

[0020] Figure 4 shows the case where the propagation path between the base station and the user terminal is a cascade path. In the case of a cascade path, the result of arranging the BIDs of the base stations in order of the magnitude of the incident power of the radio signal transmitted from the base station to the IRS matches the result of arranging the BIDs in order of the magnitude of the UE received power of the radio signal transmitted from the base station.

[0021] Figure 5 shows the case where the propagation path between the base station and the user terminal is a direct path. In the case of a direct path, the result of arranging the BIDs of the base stations in order of the magnitude of the incident power of the radio signal transmitted from the base station to the IRS does not match the result of arranging the BIDs in order of the magnitude of the UE received power of the radio signal transmitted from the base station.

[0022] Therefore, as an example of a path type discrimination method, the path type discrimination unit 11 determines whether the result of arranging the BIDs of the base stations in order of the magnitude of the incident power of the radio signals transmitted from the base stations to the IRS matches the result of arranging the BIDs in order of the magnitude of the UE received power of the radio signals transmitted from the base stations, and if the results of this determination match, it determines that the propagation path between the base station and the user terminal is a cascade path, whereas if they do not match, it determines that the propagation path between the base station and the user terminal is a direct path.

[0023] However, as shown in Fig. 6, when the user terminal is located between the base station and the IRS, the propagation path between the base station and the user terminal is a direct path, but the relationship between the incident power to the IRS and the UE received power may match, rather than being inconsistent as in Fig. 5. In this case, the accuracy of path type determination deteriorates in the path type determination method using only the relationships in Figs. 4 and 5 described above. For this reason, when the distance d_BS-UE between the base station and the user terminal calculated from the TOA between the base station and the user terminal is less than the distance d_BS-IRS between the base station and the IRS, the propagation path between the base station and the user terminal is determined to be a direct path.

[0024] FIG. 7 is a flowchart showing an example of the procedure of the path type determination method according to the present embodiment.

[0025] (Step S1) The path type discrimination unit 11 acquires the TOA between the base station and the user terminal and the UE reception power for each BID. Note that the incident power to the IRS of each BID is set in advance in the path type discrimination unit 11 as a value acquired by actual measurement or the like. Similarly, the distance d_BS-IRS between the base station and the IRS is also set in advance in the path type discrimination unit 11.

[0026] (Step S2) The path type determination unit 11 determines whether the distance d_BS-UE between the base station and the user terminal, calculated from the TOA between the base station and the user terminal, is less than the distance d_BS-IRS between the base station and the IRS. If the result of this determination is that the distance d_BS-UE is less than the distance d_BS-IRS, the process proceeds to step S3, and if not, the process proceeds to step S4.

[0027] (Step S3) The path type determination unit 11 determines that the propagation path between the base station and the user terminal is a direct path. After that, the process in FIG. 7 ends.

[0028] (Steps S4, S5, S6) The path type discrimination unit 11 judges whether or not the result of arranging the BIDs of the base stations in order of the magnitude of the power incident on the IRS matches the result of arranging the BIDs in order of the magnitude of the UE received power. If the result of the judgment shows a match, the path type discrimination unit 11 judges that the propagation path between the base station and the user terminal is a cascade path (step S5). On the other hand, if the result of the judgment shows a mismatch, the path type discrimination unit 11 judges that the propagation path between the base station and the user terminal is a direct path (step S6). After this, the processing of FIG. 7 is terminated.

[0029] The path type discrimination unit 11 acquires the reception power of each UE before and after changing the IRS state, and as a result of comparing the reception power of each UE before and after changing the IRS state, If there is a change in the UE received power, it may be determined that the propagation path between the base station and the user equipment is a cascade path. For example, the state of the IRS is the installation direction of the IRS. For example, the state of the IRS is the position of the IRS. For example, the state of the IRS is the reflection direction of the IRS.

[0030] This concludes the description of the path type determination method according to this embodiment. Returning to the description of FIG.

[0031] The environment setting unit 12 holds in advance radio environment information such as coordinates indicating the position of the base station, coordinates indicating the position of the IRS, the distance d_BS-IRS between the base station and the IRS, the incident power of each BID of the base station to the IRS, the transmission time of the radio signal of each BID of the base station, the beam direction of each BID of the base station, the reflection direction of the IRS, etc. The environment setting unit 12 sets the radio environment information in the path type determination unit 11 and the position estimation unit 14.

[0032] The information acquisition unit 13 acquires UE information such as the UE reception power and the reception time of the radio signal for each BID of the base station from the user terminal. The information acquisition unit 13 sets the UE information in the path type determination unit 11 and the position estimation unit 14.

[0033] The path type discrimination unit 11 executes the above-mentioned path type discrimination method using the radio environment information set by the environment setting unit 12 and the UE information set by the information acquisition unit 13. The TOA between the base station and the user terminal is calculated from the transmission time of the radio signal of each BID of the base station included in the radio environment information and the reception time of the radio signal of each BID of the base station included in the UE information. Note that the time is synchronized between the base station and the user terminal. Also, the method of converting the TOA into distance is set in advance in the path type discrimination unit 11.

[0034] The path type discrimination unit 11 sets the discrimination result of the type of the propagation path between the base station and the user terminal (path type discrimination result) "cascade path or direct path" in the position estimation unit .

[0035] The position estimation unit 14 estimates the position of the user terminal by the TOA positioning method, using the radio environment information set by the environment setting unit 12, the UE information set by the information acquisition unit 13, and the path type discrimination result set by the path type discrimination unit 11.

[0036] The position estimation method according to this embodiment will be described with reference to Fig. 8 and Fig. 9. Fig. 8 and Fig. 9 are diagrams for explaining the position estimation method according to this embodiment. Note that, as an example here, a main donor beam (BID1) is used among multiple beams of a base station.

[0037] (Step S101) The base station (BS1) transmits a radio signal using a main donor beam (BID1) at a transmission time t_1.

[0038] (Step S102) The user terminal receives a wireless signal through the main donor beam (BID1) at reception time "t_1+Δt_1".

[0039] (Step S103) The position estimation unit 14 calculates the distance d_1 between the base station (BS1) and the user terminal by the following formula, where c is the speed of light. d_1=c×Δt_1

[0040] (Step S104) The position estimation unit 14 calculates the distance d_IRS between the IRS and the user terminal by the following formula: d_BS1-IRS is the known distance between the base station (BS1) and the IRS. d_IRS=(c×Δt_1)-d_BS1-IRS

[0041] (Step S105) Similar to steps S101-S103, the distance d_2 between the base station (BS2) and the user terminal is calculated.

[0042] (Step S106) The position estimation unit 14 draws three circles with radii corresponding to the distances d_1, d_IRS, and d_2, as shown in FIG.

[0043] (Step S107) Based on the path type discrimination result "cascade path or direct path", the position estimation unit 14 selects two candidate points "(A, B) or (C, D)" from the four intersection points A, B, C, and D. Specifically, if the path type discrimination result is a cascade path, the position estimation unit 14 selects two candidate points "C, D". On the other hand, if the path type discrimination result is a direct path, the position estimation unit 14 selects two candidate points "A, B".

[0044] (Step S108) When the path type discrimination result is a direct path, the position estimation unit 14 selects one candidate point corresponding to the beam direction of the main donor beam (BID1) of the base station (BS1) from the two candidate points "A, B" and specifies the selected candidate point as the position of the user terminal. On the other hand, when the path type discrimination result is a cascade path, the position estimation unit 14 selects one candidate point corresponding to the beam direction of the main donor beam (BID1) of the base station (BS1) and the reflection direction of the IRS from the two candidate points "C, D" and specifies the selected candidate point as the position of the user terminal.

[0045] This concludes the description of the position estimation method according to this embodiment.

[0046] In this embodiment, the type, performance, and size of the IRS are not limited. For example, the IRS may be a liquid crystal reflector, or a diode reflector other than the liquid crystal reflector. The IRS may also include a means for acquiring the incident power of each BID from the base station, and a means for notifying the base station of the acquired incident power of each BID.

[0047] In addition, the method of acquiring the incident power to the IRS of each BID of the base station is not limited. For example, the incident power to the IRS control device may be acquired as the incident power to the IRS, or the incident power to the IRS may be acquired by other measuring devices. In addition, the incident power to the IRS of each BID of the base station may be constantly measured in real time, or the incident power to the IRS of each BID of the base station may be measured in advance when the IRS is installed.

[0048] In addition, the method of dividing the IRS when acquiring the incident power to the IRS of each BID of the base station is not limited. For example, the incident power of the entire IRS may be acquired and applied to the path type discrimination method. For example, the incident power may be acquired for each reflecting element of the IRS and applied to the path type discrimination method. For example, the incident power may be acquired for each IRS divided into a plurality of parts and applied to the path type discrimination method.

[0049] Furthermore, the location estimation method may be a method based on the TOA positioning method, and is not limited to the number or arrangement of base stations, etc. For example, the location estimation method based on the TOA positioning method may be a method that utilizes the angular characteristics of the base station antenna or IRS, the UE reception power, etc.

[0050] According to this embodiment, it is possible to determine whether the propagation path of a radio signal transmitted from a base station to a user terminal is a direct path or a cascade path. As a result, it is possible to obtain an effect that the position of a user terminal can be accurately measured by the TOA positioning method in either case, whether the user terminal is not located in the line of sight (LOS) of the base station or is located in the line of sight (LOS) of the base station.

[0051] This will, for example, make it possible to improve the overall service quality in wireless systems, thereby contributing to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is to "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0052] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not deviate from the gist of the present invention are also included.

[0053] In addition, a computer program for implementing the functions of each of the above-mentioned devices may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed. Note that the "computer system" referred to here may include hardware such as an OS and peripheral devices. In addition, if a WWW system is used, the "computer system" also includes the homepage providing environment (or display environment). In addition, the term "computer-readable recording medium" refers to writable non-volatile memory such as a flexible disk, an optical magnetic disk, a ROM, or a flash memory, a portable medium such as a DVD (Digital Versatile Disc), or a storage device such as a hard disk built into a computer system.

[0054] Furthermore, the term "computer-readable recording medium" includes devices that retain a program for a certain period of time, such as volatile memory (e.g., DRAM (Dynamic Random Access Memory)) within a computer system that serves as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. The program may be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium, or by a transmission wave in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for implementing some of the functions described above, or may be a so-called differential file (differential program) that can implement the functions described above in combination with a program already recorded in the computer system. [Explanation of symbols]

[0055] 1... positioning system, 11... path type discrimination unit, 12... environment setting unit, 13... information acquisition unit, 14... position estimation unit

Claims

1. a path type discrimination device that discriminates whether a propagation path of a radio signal transmitted from a base station to a terminal is a direct path that directly reaches the terminal from the base station, or a cascade path that reaches the terminal from the base station via a reflector, determining whether the propagation path is the direct path or the cascade path based on a comparison result between a ranking of the magnitude of the incident power of each beam of the base station to the reflector and a ranking of the magnitude of the received power of each beam of the base station at the terminal; Path type discrimination device.

2. If the distance between the base station and the terminal calculated from a TOA (Time of Arrival) between the base station and the terminal is less than the distance between the base station and the reflector, the propagation path is determined to be the direct path.

2. The path type determination device according to claim 1.

3. If the comparison result is a match, determine that the propagation path is the cascade path; If the comparison result is a mismatch, determine that the propagation path is the direct path.

3. The path type determination device according to claim 2.

4. a comparison of the received powers before and after changing the state of the reflector, and if there is a change in the received power, determining that the propagation path is the cascade path; 2. The path type determination device according to claim 1.

5. In a positioning system that measures the position of a terminal that receives a plurality of radio signals transmitted from a plurality of base stations by a Time of Arrival (TOA) positioning method, A path type determination device according to any one of claims 1 to 4, determining whether the TOA between the base station and the terminal is to be used as the TOA of a direct path or the TOA of a cascade path based on a result of the determination by the path type determination device; Positioning system.

6. A path type discrimination method for discriminating whether a propagation path of a radio signal transmitted from a base station to a terminal is a direct path that directly reaches the terminal from the base station, or a cascade path that reaches the terminal from the base station via a reflector, a path type discrimination device discriminates whether the propagation path is the direct path or the cascade path based on a comparison result between a ranking of the magnitude of the incident power of each beam of the base station to the reflector and a ranking of the magnitude of the received power of each beam of the base station at the terminal; A method for determining the path type.

7. On the computer, executing a path type discrimination step of discriminating whether a propagation path of a radio signal transmitted from a base station to a terminal is a direct path from the base station to the terminal directly or a cascade path from the base station to the terminal via a reflector; the path type discrimination step discriminates whether the propagation path is the direct path or the cascade path based on a comparison result between a ranking of the magnitude of incident power of each beam of the base station to the reflector and a ranking of the magnitude of received power of each beam of the base station at the terminal; Computer program.

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