US-20260128810-A1 - PROPAGATION ENVIRONMENT REPRODUCTION DEVICE, PROPAGATION ENVIRONMENT REPRODUCTION METHOD, AND PROPAGATION ENVIRONMENT REPRODUCTION SYSTEM

US20260128810A1US 20260128810 A1US20260128810 A1US 20260128810A1US-20260128810-A1

Abstract

There is provided a propagation environment reproduction device including: an anechoic chamber that blocks an electromagnetic wave from the outside; reconfigurable intelligent surfaces (RISs) that are installed in the anechoic chamber; a RIS control device that provides a control signal to the RISs; a transmission antenna that is installed in the anechoic chamber; a channel emulator that controls a characteristic of an electromagnetic wave transmitted from the transmission antenna; a reception antenna that is installed in the anechoic chamber as an evaluation target; and a control server that controls the RIS control device and the channel emulator. The RIS includes a first RIS that has a characteristic of changing transmittance of the electromagnetic wave according to the control signal and is disposed between the transmission antenna and the reception antenna.

Inventors

Ryotaro TANIGUCHI
Tomoki Murakami
Tomoaki Ogawa
Yasushi Takatori

Assignees

NTT, INC.

Dates

Publication Date: 20260507
Application Date: 20221004

Claims (9)

1 . A propagation environment reproduction device comprising: a reconfigurable intelligent surface (RIS) that is installed in a propagation environment reproduction space for reproducing a propagation environment of an electromagnetic wave; a RIS controller that provides a control signal to the RIS; a transmission antenna that is installed in the propagation environment reproduction space; a channel emulator that controls a characteristic of an electromagnetic wave transmitted from the transmission antenna; a reception antenna that is installed in the propagation environment reproduction space as an evaluation target; and a control server that controls the RIS controller and the channel emulator, wherein the RIS includes a first RIS that has a characteristic of changing transmittance of the electromagnetic wave according to the control signal and is disposed between the transmission antenna and the reception antenna.
2 . The propagation environment reproduction device according to claim 1 , wherein the RIS includes a sphere RIS configured by disposing the first RIS in a spherical shape so as to surround the reception antenna.
3 . The propagation environment reproduction device according to claim 1 , wherein the RIS includes a second RIS that has a characteristic of changing a reflection direction of the electromagnetic wave according to the control signal and is disposed at least one of on a wall surface, on a ceiling, or on a floor surface, or in the air of the propagation environment reproduction space.
4 . The propagation environment reproduction device according to claim 1 : wherein the RIS includes: a second RIS that has a characteristic of changing a reflection direction of the electromagnetic wave according to the control signal and is disposed at least one of on a wall surface, on a ceiling, or on a floor surface, or in the air of the propagation environment reproduction space, and a third RIS that has a characteristic of changing transmittance of the electromagnetic wave according to the control signal, the first RIS being a surface layer RIS disposed so as to overlap a surface of the second RIS.
5 . The propagation environment reproduction device according to claim 1 , wherein the propagation environment reproduction space is configured according to a specification indicated by a parameter which is set to reproduce a desired characteristic which is a propagation characteristic caused at a measurement position in a real space, the RIS and the transmission antenna are disposed according to the specification indicated by the parameter, and the control server is configured to execute: controlling the RIS controller such that the first RIS has transmittance indicated by the parameter; and controlling the channel emulator such that the transmission antenna transmits the electromagnetic wave with a characteristic indicated by the parameter.
6 . A propagation environment reproduction method for reproducing a desired propagation environment at a position of a reception antenna that is installed in a propagation environment reproduction space for reproducing a propagation environment of an electromagnetic wave by using a RIS that is installed in the propagation environment reproduction space and a transmission antenna that is installed in the propagation environment reproduction space, the RIS including a first RIS that has a characteristic of changing transmittance of the electromagnetic wave according to the control signal and is disposed between the transmission antenna and the reception antenna, the propagation environment reproduction method including: calculating, while changing parameters related to the propagation environment reproduction space, the RIS, and the transmission antenna, a propagation characteristic caused in the propagation environment reproduction space under each of said parameters by a simulation; creating a learning model that derives, when a propagation characteristic to be reproduced is provided, a parameter causing said propagation characteristic in the propagation environment reproduction space, the learning model being obtained by providing to a propagation environment model as training data a combination of an actual characteristic that is a propagation characteristic actually measured at a measurement position in a real space and a reproduction parameter that is a parameter calculated to cause a propagation characteristic which is same as the actual characteristic in the propagation environment reproduction space; causing the learning model to derive a parameter for causing a desired propagation characteristic by providing the desired propagation characteristic to the learning model; configuring the propagation environment reproduction space according to a specification indicated by the parameter derived by the learning model; disposing the RIS and the transmission antenna in the propagation environment reproduction space according to the specification indicated by the parameter derived by the learning model; controlling the first RIS such that the first RIS has transmittance indicated by the parameter derived by the learning model; and controlling a transmission signal from the transmission antenna such that the transmission antenna transmits an electromagnetic wave with a characteristic indicated by the parameter derived by the learning model.
7 . The propagation environment reproduction method according to claim 6 , wherein the RIS includes a sphere RIS configured by disposing the first RIS in a spherical shape so as to surround the reception antenna.
8 . A propagation environment reproduction system comprising: a RIS that is installed in a propagation environment reproduction space for reproducing a propagation environment of an electromagnetic wave; a transmission antenna that is installed in the propagation environment reproduction space; and a reception antenna that is installed in the propagation environment reproduction space as an evaluation target, wherein the RIS includes a first RIS that has a characteristic of changing transmittance of the electromagnetic wave according to the control signal and is disposed between the transmission antenna and the reception antenna, the propagation environment reproduction space is configured according to a specification indicated by a parameter which is set to reproduce a desired characteristic which is a propagation characteristic caused at a measurement position in a real space, the RIS and the transmission antenna are disposed according to the specification indicated by the parameter, and the propagation environment reproduction system is configured to execute: controlling the first RIS such that the first RIS has transmittance indicated by the parameter; and controlling a transmission signal from the transmission antenna such that the transmission antenna transmits an electromagnetic wave with a characteristic indicated by the parameter.
9 . The propagation environment reproduction device according to claim 2 , wherein the RIS includes a second RIS that has a characteristic of changing a reflection direction of the electromagnetic wave according to the control signal and is disposed at least one of on a wall surface, on a ceiling, or on a floor surface, or in the air of the propagation environment reproduction space.

Description

TECHNICAL FIELD The present disclosure relates to a propagation environment reproduction device, a propagation environment reproduction method, and a propagation environment reproduction system, and particularly relates to a propagation environment reproduction device, a propagation environment reproduction method, and a propagation environment reproduction system suitable for reproducing a propagation environment for verifying communication performance and the like of a measurement object. BACKGROUND ART Non Patent Literature 1 described below discloses a technology related to an over the air (OTA) test for verifying the performance and quality of a device that is used for wireless communication as a measurement object. In the OTA test, one or a plurality of transmission antennas are disposed in an anechoic chamber or a shielded room, and an environment exhibiting the same propagation characteristics as the propagation characteristics of a real space is reproduced in the space. In a case where a communication quality and the like of a measurement object are measured in a propagation environment in which the propagation characteristic occurring in a real space is reproduced, the communication quality and the like exhibited in the real space can be measured. Therefore, in a case where the OTA method is used, it is possible to easily and accurately evaluate the performance and the like of a device used for wireless communication. CITATION LIST Non Patent Literature Non Patent Literature 1: “MIMO OTA Test for a Mobile Station Performance Evaluation”, Ya Jing, Hongwei Kong, and Moray Rumney, IEEE Instrumentation & Measurement Magazine, p43-p50, June 2016 SUMMARY OF INVENTION Technical Problem Incidentally, the largest problem with implementation of the OTA test is how to accurately reproduce a desired wireless propagation environment occurring in a real space. Meanwhile, as a device that controls reflection of radio waves, a reflector called a reconfigurable intelligent surface (RIS) is known. The RIS is a reflector which uses a metamaterial technology and of which the characteristic is variable. Metamaterial means to artificially change a characteristic of a substance. According to a metamaterial technology, for example, a phenomenon in which a refractive index of an electromagnetic wave becomes a negative value may also occur. In addition, the RIS can be provided with a characteristic of making a reflection direction of the electromagnetic wave variable according to a control signal and a characteristic of making reflection power of the electromagnetic wave variable according to a control signal. In a case of performing the OTA test, if the RIS having such characteristics is installed on a ceiling, a wall surface, a floor surface, or the like of the anechoic chamber and a control signal applied to the RIS is appropriately controlled, various reflection environments can be created in the anechoic chamber. In the OTA test, it is desirable to simulate measurements in various spaces that exist in reality and measurements at various measurement positions in each real space. In a case where the RIS that makes the reflection direction and the reflection power variable is used as described above, various propagation environments can be created by setting of a single anechoic chamber. Thus, measurement efficiency can be significantly enhanced. However, as an actual propagation environment, for example, a situation is assumed in which the electromagnetic wave arrives only from the left and right of a measurement object and the electromagnetic wave does not arrive from the front of the measurement object. On the other hand, In a built-in anechoic chamber, when a transmission antenna of an electromagnetic wave and a measurement object are placed in a mutually visible arrangement, a direct path from the transmission antenna to the measurement object cannot be controlled even if an RIS that can change a reflection direction and reflection power is controlled in any way. That is, even in a case where it is desired to reduce the power of a path from a transmission direction to zero, it is not possible to prevent a direct wave from arriving at the measurement object. Under such conditions, in order to reproduce a more realistic propagation environment, it is necessary to reduce or control the power of the direct waves from the transmission antenna toward the measurement object. However, it is impossible to reproduce such an environment by combining a RIS that controls the reflection direction and a RIS that controls the reflection power. The present disclosure has been made in view of the above problems, and a first object of the present disclosure is to provide a propagation environment reproduction device capable of reproducing any propagation environment by disposing a RIS that controls direct waves in a space such as an anechoic chamber. Further, a second object of the present disclosure is to provide a propagation enviro