WO2025033248A1 - Transmission path control device, base station, terminal device, control method, and communication method - Google Patents

Abstract

Provided is a transmission path control device having a structure composed of a plurality of elements whose characteristics pertaining to the reflection or transmission of an incoming radio wave can change. The transmission path control device comprises: an acquisition unit that acquires information about a channel estimation result of each of two or more elements among the plurality of elements; and a transmission unit that transmits channel information based on information about the channel estimation result.

Description

Transmission path control device, base station, terminal device, control method, and communication method

This disclosure relates to a transmission path control device, a base station, a terminal device, a control method, and a communication method.

As demand for communications expands, the problem of radio resource depletion is becoming apparent. To address this issue, attention is being paid to technology that improves frequency utilization efficiency by dynamically changing the radio wave propagation path. Reconfigurable Intelligent Surfaces (RISs) are known as devices for changing propagation paths (hereafter also referred to as transmission path control devices). The installation of RISs makes it possible, for example, to control the direction of radio wave reflection and form new propagation paths.

JP 2022-117980 A

However, simply introducing a RIS may not fully realize effective use of radio wave resources. For example, conventionally, in order to maintain communication quality, a communication device equipped in the RIS performs channel estimation operations. However, with this conventional channel estimation method, depending on the structure of the RIS, the channel estimation results may differ from the actual channel conditions. When this happens, the quality of communication via the RIS cannot be guaranteed, and there is a possibility that radio wave resources may not be fully utilized effectively.

This disclosure therefore proposes a transmission path control device, a base station, a terminal device, a control method, and a communication method that can realize the effective use of radio wave resources.

The above problem or objective is merely one of several problems or objectives that can be solved or achieved by the multiple embodiments disclosed in this specification.

In order to solve the above problem, one embodiment of a transmission path control device according to the present disclosure is a transmission path control device having a structure composed of a plurality of elements capable of changing the characteristics related to the reflection or transmission of an incoming radio wave, and includes an acquisition unit that acquires information related to the result of channel estimation for each of two or more of the plurality of elements, and a transmission unit that transmits channel information based on the information related to the result of the channel estimation.

FIG. 2 is a diagram for explaining the structure of a RIS. FIG. 13 is a diagram showing a state in which the RIS is equipped with a communication unit. FIG. 2 is a diagram for explaining a RIS according to the present embodiment. 1 is a diagram illustrating a configuration of a communication system according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of a management device according to the present embodiment. FIG. 2 is a diagram illustrating a configuration of a base station according to the present embodiment. FIG. 1 is a diagram illustrating a configuration example of a transmission path control device according to an embodiment of the present disclosure. 2 is a diagram illustrating an example of the configuration of a surface unit included in the transmission path control device; FIG. 2 is a diagram illustrating a configuration of a terminal device according to the present embodiment. 4 is a flowchart showing a channel estimation process according to the present embodiment. FIG. 4 is a sequence diagram showing a channel estimation process according to the first embodiment. FIG. 11 is a diagram for explaining an example of the operation of a RIS. FIG. 11 is a sequence diagram showing a channel estimation process according to a second embodiment. FIG. 11 is a diagram illustrating a configuration example of a RIS according to a second embodiment. A diagram showing an example of the operation of a RIS when elements performing channel estimation for frequency band #1 and elements performing channel estimation for frequency band #2 are arranged alternately. 11 is a diagram showing an example of the operation of a RIS in the case where an element performing channel estimation for frequency band #1 and an element performing channel estimation for frequency band #2 are each arranged in half of the RIS. FIG. A diagram showing an example of the operation of a RIS when elements performing channel estimation for frequency band #1 and elements performing channel estimation for frequency band #2 are arranged in different ratios. FIG. 11 is a sequence diagram showing a channel estimation process according to a third embodiment. FIG. 13 is a sequence diagram showing a channel estimation process according to a fourth embodiment.

Below, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that in each of the following embodiments, the same parts will be designated by the same reference numerals, and duplicate descriptions will be omitted.

In addition, in this specification and drawings, multiple components having substantially the same functional configuration may be distinguished by adding different numbers after the same reference symbol. For example, multiple components having substantially the same functional configuration may be distinguished as transmission line control devices 30 ₁ , 30 ₂ , and 30 ₃ as necessary. However, when there is no particular need to distinguish between multiple components having substantially the same functional configuration, only the same reference symbol is used. For example, when there is no particular need to distinguish between the transmission line control devices 30 ₁ , 30 ₂ , and 30 ₃ , they are simply referred to as the transmission line control device 30.

One or more of the embodiments (including examples and variations) described below can be implemented independently. However, at least a portion of the embodiments described below may be implemented in appropriate combination with at least a portion of another embodiment. These embodiments may include novel features that are different from one another. Thus, these embodiments may contribute to solving different purposes or problems and may provide different effects.

The present disclosure will be described in the following order.
1. Overview 1-1. Problems 1-2. Overview of the solution 2. Configuration of the communication system 2-1. Configuration of the management device 2-2. Configuration of the base station 2-3. Configuration of the transmission path control device 2-4. Configuration of the terminal device 3. Operation of the communication system 3-1. Channel estimation process 3-2. Capability information 3-3. Channel estimation mode information 3-4. Channel information 3-5. Method of using channel information 4. Examples 4-1. Example 1
4-2. Example 2
4-3. Example 3
4-4. Example 4
5. Modifications 6. Conclusion

＜＜1. Overview＞＞
As communication demand expands, the problem of radio resource depletion has become evident. In order to address this problem, technology that improves frequency utilization efficiency by dynamically changing radio wave propagation paths has been attracting attention. Reconfigurable Intelligent Surface (RIS) is known as a device for changing propagation paths (hereinafter also referred to as a transmission path control device). RIS is also called Intelligent Reflecting Surface (IRS) or Intelligent Surface (IS).

FIG. 1 is a diagram for explaining the structure of a RIS. A RIS is a device that includes a structure (e.g., a reflector) that is composed of one or more metasurface elements that can dynamically control the permittivity and/or permeability. A metasurface element is a type of artificial medium (metamaterial) that realizes any permittivity and/or permeability by periodically arranging structures that are small relative to the wavelength. A metasurface element is sometimes simply called a metasurface. A RIS can control the amplitude, phase, polarization, or frequency of an incoming radio wave by manipulating the permittivity and/or permeability of the metasurface (metasurface element). A control device inside or outside the RIS can control the reflected wave of the RIS to control the direction of the reflected wave to bypass an obstruction or form a new propagation path.

<1-1. Issues>
The introduction of the RIS is expected to improve frequency utilization efficiency. However, simply introducing the RIS may not fully realize effective utilization of radio wave resources. For example, in a conventional RIS, a communication device (e.g., a communication unit shown in FIG. 2) included in the RIS performs an operation for channel estimation (e.g., a sounding operation). FIG. 2 is a diagram showing a state in which the RIS is provided with a communication unit. For example, in a conventional RIS, a communication unit included in the RIS performs a sounding operation of a channel between a base station and the RIS or between a terminal device and the RIS, and feeds back the sounding result to the base station or the terminal device as a channel estimation result.

However, with this conventional channel estimation method, depending on the structure of the RIS (e.g., the shape/size of the RIS), the channel estimation results may deviate from the actual channel conditions. For example, if the size of the RIS is large, the channel information acquired by the sounding operation of the communication unit may deviate significantly from the actual channel conditions. When this happens, the quality of communication via the RIS cannot be guaranteed, and there is a possibility that radio wave resources will not be fully utilized effectively.

<1-2. Overview of the solution>
Therefore, in this embodiment, the above problem is solved as follows.

The communication system of this embodiment includes one or more communication devices (e.g., base stations and/or terminal devices) and one or more RISs. FIG. 3 is a diagram for explaining the RIS of this embodiment. The RIS includes multiple elements (metasurface elements shown in FIG. 3) that can change the characteristics related to the reflection or transmission of incoming radio waves. In the RIS of this embodiment, in addition to a phase shifter that manipulates the reflected wave/transmitted wave, a channel estimation unit is arranged in each of two or more of the multiple elements, as shown in FIG. 3, for example. The elements in which the channel estimation unit is arranged may be all of the multiple elements included in the RIS, or may be some of the multiple elements. In addition, a secondary modulation unit and/or an amplifier may be arranged in the phase shifter.

The channel estimation unit performs operations related to channel estimation (e.g., sounding operations) at the arranged elements based on a channel estimation signal transmitted from the base station or terminal device. The RIS control device obtains information related to the results of channel estimation from each channel estimation unit. The RIS control device then transmits channel information generated based on the information related to the results of channel estimation to the base station or terminal device.

This makes it possible to perform channel estimation for each element. As a result, more accurate channel estimation becomes possible, allowing the RIS to more precisely control elements or form reflected beams. As a result, the base station/terminal device can perform high-quality communications via the RIS, realizing more efficient use of radio wave resources.

　The above is an overview of this embodiment, but the communication system 1 of this embodiment will be described in detail below.

<<2. Configuration of communication system>>
First, a specific description will be given of the configuration of the communication system 1. The configuration of the communication system 1 shown below is common to the first to fourth embodiments.

FIG. 4 is a diagram showing the configuration of a communication system 1 according to this embodiment. As shown in FIG. 4, the communication system 1 includes a management device 10, a base station 20, a transmission line control device 30, and a terminal device 40. Note that the communication system 1 may include devices other than those shown in FIG. 4. For example, the communication system 1 may include a control station that controls the transmission line control device 30. The control station may centrally control multiple transmission line control devices 30. Note that the control device for the multiple transmission line control devices 30 is typically a control unit (e.g., a processor) included in the transmission line control device 30. However, the control station can also be considered as a control device for the transmission line control device 30.

The communication system 1 provides users with a wireless network (mobile network) that enables mobile communication by having each wireless communication device that constitutes the communication system 1 work in cooperation with one another. The wireless network of this embodiment may be, for example, a cellular network composed of a radio access network RAN and a core network CN. The mobile network may include terminal device 40. In this embodiment, the wireless communication device is a communication device that has a wireless communication function, and in the example of FIG. 4, this corresponds to base station 20 and terminal device 40.

The communication system 1 may include a plurality of management devices 10, base stations 20, transmission line control devices ₃₀ , and terminal devices 40. In the example of Fig. 4, the communication system 1 includes management devices 10-1 and _10-2 as the management devices 10, and includes base stations _20-1 , _20-2 , and _20-3 as the base stations 20. In the example of Fig. 4, the communication system 1 includes transmission line control devices _30-1 , _30-2 , and _30-3 as the transmission line control devices 30, and includes terminal devices _40-1 , _40-2 , and _40-3 as the terminal devices 40.

The terminal device 40 may be configured to connect to a network using a radio access technology (RAT: Radio Access Technology) such as LTE (Long Term Evolution), NR (New Radio), 6G, Wi-Fi, Bluetooth (registered trademark), etc. In this case, the terminal device 40 may be configured to be able to use different radio access technologies (wireless communication methods). For example, the terminal device 40 may be configured to be able to use NR and Wi-Fi. The terminal device 40 may also be configured to be able to use different cellular communication technologies (e.g., LTE, NR, or 6G). In the following description, the terminal device 40 may be referred to as UE (User Equipment).

LTE and NR are types of cellular communication technologies that enable mobile communication for terminal devices by arranging multiple areas covered by base stations in the form of cells. 6G, also a type of cellular communication technology, has the potential to become a technology that enables mobile communication for terminal devices by arranging multiple areas covered by base stations in the form of cells.

In the following description, "LTE" includes LTE-A (LTE-Advanced), LTE-A Pro (LTE-Advanced Pro), and EUTRA (Evolved Universal Terrestrial Radio Access). NR includes NRAT (New Radio Access Technology) and FEUTRA (Further EUTRA). A single base station 20 may manage multiple cells. In the following description, a cell that supports LTE is referred to as an LTE cell, and a cell that supports NR is referred to as an NR cell.

NR is the next generation (5th generation) radio access technology after LTE (4th generation communication including LTE-Advanced and LTE-Advanced Pro). NR is a radio access technology that can support various use cases including eMBB (Enhanced Mobile Broadband), mMTC (Massive Machine Type Communications) and URLLC (Ultra-Reliable and Low Latency Communications). NR was standardized in 3GPP (registered trademark) Rel-15 as a technical framework that supports the usage scenarios, requirements, and deployment scenarios in these use cases. Furthermore, Beyond 5G and 6G requires the simultaneous realization of multiple axes of high speed, large capacity, low latency, high reliability, and multiple simultaneous connections.

6G is the next generation of cellular communication technology after NR and 5GS (5G system), which are the fifth generation mobile communications. 6G includes radio access technology and network technology between base stations, core networks, and data networks. 6G also includes technology for the advancement (extreme connectivity) of eMBB, mMTC, and URLLC, which were the main use cases or requirements of NR. 6G also includes new technologies in new aspects. For example, 6G may include technologies related to AI (cognitive network, AI native Air Interface), sensing (including radar sensing and network as a sensor), and terahertz communication.

The wireless network may be compatible with at least one of radio access technologies (RATs) such as LTE (Long Term Evolution), NR (New Radio), and 6G. LTE, NR, and 6G are types of cellular communication technologies that enable mobile communication for terminal devices by arranging multiple areas covered by base stations in the form of cells. The wireless access method used by the communication system 1 is not limited to LTE, NR, and 6G, and may be other wireless access methods such as W-CDMA (Wideband Code Division Multiple Access) and cdma2000 (Code Division Multiple Access 2000).

Furthermore, the base station 20 may be a terrestrial station or a non-terrestrial station. The non-terrestrial station may be a satellite station or an aircraft station. If the non-terrestrial station is a satellite station, the wireless network may be a bent-pipe (transparent) type mobile satellite communication system.

In this embodiment, the terrestrial station and terrestrial base station refer to base stations and relay stations installed on the ground. Here, "terrestrial" has a broad definition of terrestrial, including not only land but also underground, on water, and underwater. In the following description, the term "terrestrial station" may be replaced with "gateway."

Note that LTE base stations are sometimes referred to as eNodeB (Evolved Node B) or eNB. NR base stations are sometimes referred to as gNodeB or gNB. 6G base stations are sometimes referred to as 6G NodeB (6GNB). In LTE, NR, and 6G, terminal devices (also called mobile stations or terminals) are sometimes referred to as UE (User Equipment). Note that terminal devices are a type of communication device and are also called mobile stations or terminals.

In addition, the terminal device 40 may be able to connect to the network using a wireless access technology (wireless communication method) other than LTE, NR, 6G, Wi-Fi, and Bluetooth. For example, the terminal device 40 may be able to connect to the network using LPWA (Low Power Wide Area) communication. In addition, the terminal device 40 may be able to connect to the network using a proprietary wireless communication standard.

Here, LPWA communication refers to wireless communication that enables wide-range communication with low power. For example, LPWA wireless refers to IoT (Internet of Things) wireless communication that uses a specific low-power radio (e.g., 920 MHz band) or an ISM (Industry-Science-Medical) band. The LPWA communication used by the terminal device 40 may be compliant with the LPWA standard. Examples of LPWA standards include ELTRES, ZETA, SIGFOX, LoRaWAN, and NB-IoT. Of course, the LPWA standard is not limited to these, and other LPWA standards may also be used.

Each wireless communication device shown in FIG. 4 may be considered as a device in a logical sense. That is, a part of each wireless communication device may be realized by a virtual machine (VM), a container such as Docker, etc., and these may be implemented on the same physical hardware.

In this embodiment, the concept of a wireless communication device includes not only portable mobile devices (terminal devices) such as mobile terminals, but also devices installed in structures or mobile bodies. The structures or mobile bodies themselves may be considered wireless communication devices. The concept of a wireless communication device also includes not only terminal devices 40, but also base stations 20. A wireless communication device is a type of processing device or information processing device. A wireless communication device can also be referred to as a transmitting device or a receiving device.

Below, the configuration of each wireless communication device that constitutes communication system 1 will be specifically described. Note that the configuration of each wireless communication device shown below is merely an example. The configuration of each wireless communication device may be different from the configuration shown below.

2-1. Configuration of management device
First, the configuration of the management device 10 will be described.

The management device 10 is an information processing device (computer) that manages a wireless network. For example, the management device 10 is an information processing device that manages communications of the base station 20. The management device 10 is also a type of communication device.

The management device 10 may be, for example, a device having a function as an MME (Mobility Management Entity). The management device 10 may also be a device having a function as an AMF (Access and Mobility Management Function) and/or an SMF (Session Management Function). The MME, AMF, and SMF are control plane network function nodes in the core network. The management device 10 may be a device having a function as a control plane network function (6G CPNF) in 6G. The 6G CPNF may be composed of one or more logical nodes.

Of course, the functions of the management device 10 are not limited to MME, AMF, SMF, and 6G CPNF. The management device 10 may be a device having functions as NSSF (Network Slice Selection Function), AUSF (Authentication Server Function), PCF (Policy Control Function), and UDM (Unified Data Management). The management device 10 may also be a device having functions as HSS (Home Subscriber Server).

The management device 10 may also have a gateway function. For example, the management device 10 may have a function as an S-GW (Serving Gateway) or a P-GW (Packet Data Network Gateway). The management device 10 may also have a UPF (User Plane Function) function. In this case, the management device 10 may have multiple UPFs. The management device 10 may also be a device that has a function as a User Plane Network Function (6G UPNF) in 6G.

The core network is composed of multiple network functions, and each network function may be consolidated into one physical device or distributed across multiple physical devices. In other words, the management device 10 may be distributed across multiple devices. Furthermore, this distributed arrangement may be controlled so that it is executed dynamically. The base station 20 and the management device 10 form a single network, and provide wireless communication services to the terminal device 40. The management device 10 is connected to the Internet, and the terminal device 40 can use various services provided over the Internet via the base station 20.

Note that the management device 10 does not necessarily have to be a device that constitutes a core network. For example, the core network may be a W-CDMA (Wideband Code Division Multiple Access) or cdma2000 (Code Division Multiple Access 2000) core network. In this case, the management device 10 may be a device that functions as an RNC (Radio Network Controller).

FIG. 5 is a diagram showing the configuration of a management device 10 according to this embodiment. The management device 10 includes a communication unit 11, a storage unit 12, and a control unit 13. The configuration shown in FIG. 5 is a functional configuration, and the hardware configuration may be different from this. Furthermore, the functions of the management device 10 may be statically or dynamically distributed and implemented in multiple physically separated configurations. The management device 10 may be composed of multiple server devices.

The communication unit 11 is a communication interface for communicating with other communication devices (e.g., base station 20). The communication unit 11 may be a network interface or a device connection interface. The communication unit 11 may be a LAN (Local Area Network) interface such as a NIC (Network Interface Card), or a Universal Serial Bus (USB) interface configured by a USB host controller or a USB port. The communication unit 11 may be a wired interface or a wireless interface. The communication unit 11 functions as a communication means for the management device 10. The communication unit 11 is controlled by the control unit 13.

The memory unit 12 is a readable and writable storage device such as a dynamic random access memory (DRAM), a static random access memory (SRAM), a flash memory, or a hard disk. The memory unit 12 functions as a storage means of the management device 10. The memory unit 12 stores, for example, the connection state of the terminal device 40. The memory unit 12 stores the state of the RRC (Radio Resource Control) of the terminal device 40 and the ECM (EPS Connection Management), or the state of the 5G System CM (Connection Management). The memory unit 12 may function as a home memory that stores the location information of the terminal device 40. The memory unit 12 also stores a learning model (prediction model) for predicting the future quality of the mobile network. The learning model will be described later.

The control unit 13 is a controller that controls each part of the management device 10. The control unit 13 may be realized by a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). In detail, the control unit 13 may be realized by a processor executing various programs stored in a storage device inside the management device 10 using a RAM (Random Access Memory) or the like as a working area. The control unit 13 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The control unit 13 may also be realized by a GPU (Graphics Processing Unit). The CPU, MPU, ASIC, FPGA, and GPU can all be considered as controllers. The control unit 13 may be composed of multiple physically separated objects. For example, the control unit 13 may be composed of multiple semiconductor chips.

The operation of the control unit 13 may be similar to the operation of the control unit 23 of the base station 20 and the control unit 43 of the terminal device 40.

<2-2. Base station configuration>
Next, the configuration of the base station 20 will be described.

The base station 20 is a wireless communication device that performs wireless communication with other wireless communication devices (e.g., a terminal device 40 or another base station 20). The base station 20 may perform wireless communication with the terminal device 40 via a relay station, or may perform wireless communication directly with the terminal device 40.

The base station 20 is a device equivalent to a wireless base station (Base Station, Node B, eNB, gNB, 6GNB, etc.) or a wireless access point (Access Point). The base station 20 may be a wireless relay station. The base station 20 may be an optical extension device called an RRH (Remote Radio Head). The base station 20 may be a receiving station such as an FPU (Field Pickup Unit). The base station 20 may be an IAB (Integrated Access and Backhaul) donor node or an IAB relay node that provides wireless access lines and wireless backhaul lines by time division multiplexing, frequency division multiplexing, or space division multiplexing.

The wireless access technology used by the base station 20 may be cellular communication technology. The wireless access technology used by the base station 20 may be wireless LAN technology. The wireless access technology used by the base station 20 may be LPWA (Low Power Wide Area) communication technology. However, the wireless access technology used by the base station 20 is not limited to these, and may be other wireless access technology. The wireless communication used by the base station 20 may be wireless communication using millimeter waves, or wireless communication using terahertz waves. The wireless communication used by the base station 20 may be wireless communication using radio waves, or wireless communication using infrared or visible light (optical wireless). In addition, the base station 20 may be capable of NOMA (Non-Orthogonal Multiple Access) communication with the terminal device 40. Here, NOMA communication refers to communication (transmission, reception, or both) using non-orthogonal resources. In addition, the base station 20 may be capable of NOMA communication with other base stations 20.

The base station 20 may be able to communicate with the core network via a base station-core network interface (e.g., NG Interface, S1 Interface, etc.). This interface may be either wired or wireless. The base station may be able to communicate with other base stations via a base station-to-base station interface (e.g., Xn Interface, X2 Interface, F1 Interface, etc.). This interface may be either wired or wireless.

The concept of a base station (also called "base station equipment") includes not only donor base stations but also relay base stations (also called "relay stations"). A relay base station may be any one of the following: RF Repeater, Smart Repeater, or Intelligent Surface. The concept of a base station includes not only a structure with base station functions, but also equipment installed in the structure.

Structures include, for example, high-rise buildings, houses, steel towers, station facilities, airport facilities, port facilities, office buildings, school buildings, hospitals, factories, commercial facilities, stadiums, and other buildings. The concept of a structure includes not only buildings, but also non-building structures such as tunnels, bridges, dams, fences, and steel pillars, as well as equipment such as cranes, gates, and windmills. The concept of a structure includes not only land (ground in the narrow sense) or underground structures, but also structures on water such as piers or megafloats, and underwater structures such as marine observation facilities. A base station can also be referred to as an information processing device.

The base station 20 may be a donor station or a relay station (relay station). The base station 20 may be a fixed station or a mobile station. A mobile station is a wireless communication device (e.g., a base station) that is configured to be mobile. In this case, the base station 20 may be a device installed on a mobile body, or may be the mobile body itself. For example, a relay station with mobility can be considered as the base station 20 as a mobile station. In addition, devices that are originally mobile and have the functions of a base station (at least part of the functions of a base station), such as vehicles, UAVs (Unmanned Aerial Vehicles) represented by drones, and smartphones, also fall under the category of the base station 20 as a mobile station.

Here, the moving body may be a mobile terminal such as a smartphone or a mobile phone. The moving body may be a moving body that moves on land (ground in the narrow sense) (e.g., a vehicle such as a car, bicycle, bus, truck, motorcycle, train, or linear motor car), or a moving body that moves underground (e.g., inside a tunnel) (e.g., a subway). The moving body may also be a moving body that moves on water (e.g., a ship such as a passenger ship, cargo ship, or hovercraft), or a moving body that moves underwater (e.g., a submarine such as a submarine, submarine, or unmanned submersible). The moving body may also be a moving body that moves within the atmosphere (e.g., an aircraft such as an airplane, airship, or drone).

The base station 20 may be a terrestrial base station (ground station) installed on the ground. The base station 20 may be a base station located on a structure on the ground, or a base station installed on a mobile object moving on the ground. The base station 20 may be an antenna installed on a structure such as a building and a signal processing device connected to that antenna. The base station 20 may be the structure or the mobile object itself. "Ground" refers not only to land (ground in the narrow sense) but also to ground, on water, and underwater in a broad sense. The base station 20 is not limited to a terrestrial base station. If the communication system 1 is a satellite communication system, the base station 20 may be an aircraft station. From the perspective of the satellite station, an aircraft station located on the earth is a ground station.

The base station 20 is not limited to a ground station. The base station 20 may be a non-terrestrial base station device (non-terrestrial station) that can float in the air or space. The base station 20 may be an aircraft station or a satellite station.

The satellite station is a satellite station capable of floating outside the atmosphere. The satellite station may be a device mounted on a space vehicle such as an artificial satellite, or may be the space vehicle itself. The space vehicle is a vehicle that moves outside the atmosphere. Examples of space vehicles include artificial celestial bodies such as artificial satellites, spacecraft, space stations, and probes. Note that a satellite that becomes a satellite station may be any of a low earth orbit (LEO: Low Earth Orbiting) satellite, a medium earth orbit (MEO: Medium Earth Orbiting) satellite, a geostationary (GEO: Geostationary Earth Orbiting) satellite, or a highly elliptical orbit (HEO: Highly Elliptical Orbiting) satellite. The satellite station may be a device mounted on a low earth orbit satellite, a medium earth orbit satellite, a geostationary satellite, or a highly elliptical orbit satellite.

An aircraft station is a wireless communication device capable of floating in the atmosphere of an aircraft or the like. An aircraft station may be a device mounted on an aircraft or the like, or it may be the aircraft itself. The concept of an aircraft includes not only heavier than air vehicles such as airplanes or gliders, but also lighter than air vehicles such as balloons or airships. The concept of an aircraft includes not only heavier than air vehicles or lighter than air vehicles, but also rotorcraft such as helicopters or autogyros. An aircraft station, or an aircraft equipped with an aircraft station, may be an unmanned aerial vehicle such as a drone.

The concept of unmanned aerial vehicles also includes unmanned aerial systems (UAS) and tethered UAS. The concept of unmanned aerial vehicles also includes lighter than air UAS (LTA) and heavy unmanned aerial systems (HTA). The concept of unmanned aerial vehicles also includes high altitude UAS platforms (HAPs).

The size of the coverage of the base station 20 may be relatively large, such as a macrocell, or relatively small, such as a picocell. The size of the coverage of the base station 20 may be extremely small, such as a femtocell. The base station 20 may have a beamforming function. The base station 20 may form a cell or service area for each beam. Additionally or alternatively, the base station 20 may have a function to deliver a desired wave to a specific point with pinpoint accuracy by further taking into account distance information from the antenna of the base station 20, in addition to beamforming, which gives directionality to the beam. This function may be called beam focusing or point forming.

FIG. 6 is a diagram showing the configuration of a base station 20 according to this embodiment. The base station 20 includes a wireless communication unit 21, a storage unit 22, a control unit 23, and a sensor unit 24. The base station 20 does not necessarily have to include all of these components. For example, the base station 20 does not necessarily have to include the sensor unit 24. Note that the configuration shown in FIG. 6 is a functional configuration, and the hardware configuration may differ from this. Furthermore, the functions of the base station 20 may be implemented in a distributed manner across multiple physically separated components.

The wireless communication unit 21 is a signal processing unit for wireless communication with other wireless communication devices (e.g., terminal device 40 or other base station 20). The wireless communication unit 21 is controlled by the control unit 23. The wireless communication unit 21 supports one or more wireless access methods. The wireless communication unit 21 may support at least one of NR, LTE, and 6G. In addition to NR, LTE, and 6G, the wireless communication unit 21 may support W-CDMA, cdma2000, etc. The wireless communication unit 21 may support automatic retransmission technology such as HARQ (Hybrid Automatic Repeat reQuest).

The wireless communication unit 21 includes a transmission processing unit 211, a reception processing unit 212, and an antenna 213. The wireless communication unit 21 may include a plurality of transmission processing units 211, reception processing units 212, and antennas 213. When the wireless communication unit 21 supports a plurality of wireless access methods, each unit of the wireless communication unit 21 may be configured separately for each wireless access method. The transmission processing unit 211 and the reception processing unit 212 may be configured separately for LTE, NR, and 6G. The antenna 213 may be configured with a plurality of antenna elements, for example, a plurality of patch antennas. The wireless communication unit 21 may have a beamforming function. For example, the wireless communication unit 21 may have a polarized beamforming function using vertical polarization (V polarization) and horizontal polarization (H polarization) (or a polarized beamforming function using dual polarization in polarization directions of 45 degrees and -45 degrees from the vertical direction).

The transmission processing unit 211 performs transmission processing of the downlink control information and the downlink data. For example, the transmission processing unit 211 performs encoding of the downlink control information and the downlink data input from the control unit 23 using an encoding method such as block encoding, convolution encoding, turbo encoding, or the like. Here, the encoding may be performed using a polar code or a low density parity check code (LDPC code). Then, the transmission processing unit 211 modulates the encoded bits using a predetermined modulation method such as BPSK, QPSK, 16QAM, 64QAM, 256QAM, or the like. In this case, the signal points on the constellation do not necessarily have to be equidistant. The constellation may be a non-uniform constellation (NUC: Non Uniform Constellation). Then, the transmission processing unit 211 multiplexes the modulation symbols of each channel and the downlink reference signal, and places them in a predetermined resource element. Then, the transmission processing unit 211 performs various signal processing on the multiplexed signal. For example, the transmission processing unit 211 performs processes such as conversion to the frequency domain using a fast Fourier transform, addition of a guard interval (cyclic prefix), generation of a baseband digital signal, conversion to an analog signal, quadrature modulation, up-conversion, removal of unnecessary frequency components, and power amplification. The signal generated by the transmission processing unit 211 is transmitted from an antenna 213.

The reception processing unit 212 processes the uplink signal received via the antenna 213. For example, the reception processing unit 212 performs down-conversion, removal of unnecessary frequency components, control of amplification level, orthogonal demodulation, conversion to a digital signal, removal of guard intervals (cyclic prefixes), extraction of frequency domain signals by fast Fourier transform, etc., on the uplink signal. Then, the reception processing unit 212 separates uplink channels such as PUSCH (Physical Uplink Shared Channel) and PUCCH (Physical Uplink Control Channel) and uplink reference signals from the signal that has been subjected to these processes. In addition, the reception processing unit 212 demodulates the received signal using a modulation method such as BPSK (Binary Phase Shift Keying) and QPSK (Quadrature Phase Shift Keying) for the modulation symbols of the uplink channel. The modulation method used for demodulation may be 16QAM (Quadrature Amplitude Modulation), 64QAM, or 256QAM. In this case, the signal points on the constellation do not necessarily have to be equidistant. The constellation may be a non-uniform constellation (NUC). Then, the reception processing unit 212 performs a decoding process on the coded bits of the demodulated uplink channel. The decoded uplink data and uplink control information are output to the control unit 23.

The antenna 213 is an antenna device that converts electric current and radio waves into each other. The antenna 213 may be composed of one antenna element, for example, one patch antenna. The antenna 213 may be composed of multiple antenna elements, for example, multiple patch antennas. When the antenna 213 is composed of multiple antenna elements, the wireless communication unit 21 may have a beamforming function. The wireless communication unit 21 may be configured to generate a directional beam by controlling the directivity of the wireless signal using multiple antenna elements. The antenna 213 may be a dual polarized antenna. When the antenna 213 is a dual polarized antenna, the wireless communication unit 21 may use vertical polarization (V polarization) and horizontal polarization (H polarization) (or dual polarization with polarization directions of 45 degrees and -45 degrees from the vertical direction) when transmitting a wireless signal. The wireless communication unit 21 may control the directivity of the wireless signal transmitted using vertical polarization and horizontal polarization (or dual polarization with polarization directions of 45 degrees and -45 degrees from the vertical direction). Additionally, the wireless communication unit 21 may transmit and receive spatially multiplexed signals via multiple layers consisting of multiple antenna elements.

The memory unit 22 is a readable and writable storage device such as a DRAM, an SRAM, a flash memory, or a hard disk. The memory unit 22 functions as a storage means for the base station 20.

The control unit 23 is a controller that controls each part of the base station 20. The control unit 23 controls the wireless communication unit so as to perform wireless communication with other wireless communication devices (e.g., the terminal device 40 or another base station 20). The control unit 23 may be realized by a processor such as a CPU or an MPU. Specifically, the control unit 23 may be realized by a processor executing various programs stored in a storage device inside the base station 20 using a RAM or the like as a working area. The control unit 23 may be realized by an integrated circuit such as an ASIC or an FPGA. The control unit 23 may also be realized by a GPU. The CPU, MPU, ASIC, FPGA, and GPU can all be considered as controllers. The control unit 23 may be composed of multiple physically separated objects. For example, the control unit 23 may be composed of multiple semiconductor chips.

The control unit 23 includes an acquisition unit 231, a transmission unit 232, and a communication control unit 233. Each block constituting the control unit 23 (acquisition unit 231 to communication control unit 233) is a functional block indicating a function of the control unit 23. These functional blocks may be software blocks or hardware blocks. For example, each of the above-mentioned functional blocks may be a software module realized by software (including a microprogram), or may be a circuit block on a semiconductor chip (die). Of course, each functional block may be a processor or an integrated circuit. The control unit 23 may be configured in functional units different from the above-mentioned functional blocks. The method of configuring the functional blocks is arbitrary.

The operation of each block constituting the control unit 23 may be similar to the operation of each block provided in the control unit 43 of the terminal device 40. The operation of the control unit 23 may be similar to the operation of the control unit 13 of the management device 10.

The sensor unit 24 is a sensor that acquires various information related to wireless communication. For example, the sensor unit 24 is a sensor that acquires information about objects around the device. For example, the sensor unit 24 is a sensor that acquires information about the position, shape, movement, etc. of other objects (for example, a third object, a communication device that constitutes a communication link, or a third communication device). The sensor unit 24 may be a sensor for detecting the state of the device itself (for example, the position, movement speed, inclination, vibration, rotation, etc. of the base station 20).

The sensor unit 24 is a sensor that acquires various information related to wireless communication. For example, the sensor unit 24 is a sensor that acquires information about objects around the device. For example, the sensor unit 24 is a sensor that acquires information about the position, shape, movement, etc. of other objects. The sensor unit 24 may be a sensor for detecting the state of the device itself (for example, the position, movement speed, inclination, vibration, rotation, etc. of the base station 20).

The sensor unit 24 may be an RF sensor (Radio Frequency Sensor) or a non-RF sensor. The sensor unit 24 may also be a sensor system (e.g., a sensor unit or a sensor module) that combines an RF sensor and a non-RF sensor.

Here, an RF sensor refers to a component that uses radio waves for measurement. An example of an RF sensor is a radar that uses radio waves such as millimeter waves. In this case, the radio waves used by the radar are not limited to radio waves in the millimeter wave band (e.g., 30 to 300 GHz band), but may be, for example, radio waves in the microwave band (e.g., 3 to 30 GHz band) or quasi-millimeter wave band (e.g., 20 to 30 GHz band).

Another example of an RF sensor is a wireless positioning sensor (wireless positioning system). An example of a wireless positioning sensor is a GNSS (Global Navigation Satellite System) sensor. Here, the GNSS sensor may be a GPS (Global Positioning System) sensor, a GLONASS sensor, a Galileo sensor, or a QZSS (Quasi-Zenith Satellite System) sensor. Note that the wireless positioning sensor is not limited to a GNSS sensor, and may be, for example, a sensor for 3GPP positioning or Wi-Fi/Bluetooth positioning.

A non-RF sensor is a component that performs measurements without using radio waves. An example of a non-RF sensor is a distance measurement sensor (ranging system) such as LiDAR (Light Detection and Ranging). In this case, the light used by the distance measurement sensor (e.g., laser light) is not limited to visible light, and may be invisible light such as ultraviolet light, infrared light, or near-infrared light. Another example of a non-RF sensor is sonar that uses sound waves such as ultrasound.

Another example of a non-RF sensor is a camera. The camera is not limited to a visible light camera. For example, the camera may be a near-infrared camera, a mid-infrared camera, or a far-infrared camera. The camera may be a monocular camera or a stereo camera. Another example of a non-RF sensor may be an image sensor. In this case, the image sensor may have image plane phase difference pixels embedded discretely. Additionally, the sensor unit 24 may be a ToF (Time of Flight) sensor or a microphone.

Other examples of non-RF sensors include acceleration sensors (e.g., 3-axis acceleration sensors), speed sensors, gyro sensors, IMUs (Inertial Measurement Units), and other motion sensors. Other examples of non-RF sensors include magnetic sensors, barometers, and altimeters (e.g., barometers).

The sensor unit 24 may also be a sensor that acquires various information for predicting the quality of a communication path (e.g., a communication path formed by a wireless communication unit). For example, the sensor unit 24 is a sensor that detects the reception S/N ratio of radio waves received from another communication device (e.g., a communication device that is the communication partner, or a communication device other than the communication partner). Of course, the information acquired by the sensor unit 24 is not limited to the reception S/N ratio, as long as it can be used to predict the quality of the communication path.

Of course, the sensor unit 24 is not limited to the above-mentioned sensors. The sensor unit 24 may also be a sensor system that combines multiple sensors described above.

In some embodiments, the base station 20 may be configured as a collection of multiple physical or logical devices. As an example, the base station 20 of this embodiment may be divided into multiple devices such as a BBU (Baseband Unit) and an RU (Radio Unit). The base station 20 may be interpreted as a collection of these multiple devices. Furthermore, the base station may be either a BBU or an RU, or both. The BBU and the RU may be connected by a specified interface, such as eCPRI (enhanced Common Public Radio Interface).

The RU may be referred to as an RRU (Remote Radio Unit) or an RD (Radio DoT). The RU may correspond to a gNB-DU (gNB Distributed Unit) described later. The BBU may correspond to a gNB-CU (gNB Central Unit) described later. The RU may be a device formed integrally with an antenna. The antenna of the base station 20, for example an antenna formed integrally with the RU, may employ an Advanced Antenna System and support, for example, MIMO such as FD-MIMO or beamforming. The antenna of the base station 20 may have, for example, 64 transmitting antenna ports and 64 receiving antenna ports.

The antenna mounted on the RU may be an antenna panel composed of one or more antenna elements, and the RU may be equipped with one or more antenna panels. The RU may be equipped with two types of antenna panels, a horizontally polarized antenna panel and a vertically polarized antenna panel. The RU may be equipped with two types of antenna panels, a right-hand circularly polarized antenna panel and a left-hand circularly polarized antenna panel, or an antenna panel with a polarization direction of 45 degrees from the vertical direction and an antenna panel with a polarization direction of -45 degrees. Multiple antennas with these multiple polarization directions may be mounted on a single antenna panel. The RU may form and control an independent beam for each antenna panel.

Multiple base stations 20 may be connected to each other. One or more base stations 20 may be included in a radio access network (RAN: Radio Access Network). In this case, the base station 20 may be simply referred to as a RAN, a RAN node, an AN (Access Network), or an AN node. The RAN in LTE may be called EUTRAN (Enhanced Universal Terrestrial RAN). The RAN in NR may be called NGRAN. Also, the RAN in 6G may be called 6GRAN. The RAN in W-CDMA (UMTS) may be called UTRAN.

The LTE base station 20 may be referred to as an eNodeB (Evolved Node B) or eNB. In this case, the EUTRAN includes one or more eNodeBs (eNBs). The NR base station 20 may be referred to as a gNodeB or gNB. In this case, the NGRAN includes one or more gNBs. The 6G base station may be referred to as a 6GNodeB, 6gNodeB, 6GNB, or 6gNB. In this case, the 6GRAN includes one or more 6GNBs. The EUTRAN may include a gNB (en-gNB) connected to a core network (EPC) in the LTE communication system (EPS). The NGRAN may include an ng-eNB connected to a core network 5GC in the 5G communication system (5GS).

When the base station 20 is an eNB, gNB, 6GNB, etc., the base station 20 may be referred to as a 3GPP access. When the base station 20 is a wireless access point, the base station 20 may be referred to as a non-3GPP access. The base station 20 may be a radio extension device called an RRH (Remote Radio Head). When the base station 20 is a gNB, the base station 20 may be a combination of the gNB-CU and gNB-DU described above, or may be either a gNB-CU or a gNB-DU.

Here, the gNB-CU hosts multiple upper layers (e.g., RRC (Radio Resource Control), SDAP (Service Data Adaptation Protocol), PDCP (Packet Data Convergence Protocol)) in the access stratum for communication with the UE. On the other hand, the gNB-DU hosts multiple lower layers (e.g., RLC (Radio Link Control), MAC (Medium Access Control), PHY (Physical Access Control)) in the access stratum. That is, among the messages/information described below, RRC signaling (semi-static notification) may be generated by the gNB-CU, while MAC CE and DCI (dynamic notification) may be generated by the gNB-DU. Alternatively, among the RRC configurations (semi-static notification), some configurations such as IE:cellGroupConfig may be generated by the gNB-DU, and the remaining configurations may be generated by the gNB-CU. These configurations may be transmitted and received over the F1 interface described below.

The base station 20 may be configured to be able to communicate with other base stations. When the multiple base stations 20 are eNBs or a combination of eNBs and en-gNBs, the base stations 20 may be connected to each other via an X2 interface. When the multiple base stations 20 are gNBs or a combination of gn-eNBs and gNBs, the base stations 20 may be connected to each other via an Xn interface. When the multiple base stations 20 are a combination of gNB-CUs and gNB-DUs, the base stations 20 may be connected to each other via the F1 interface described above. Messages/information (e.g., RRC signaling, MAC CE (MAC Control Element), or DCI (Downlink Control Information), etc.) described later may be transmitted between the multiple base stations 20, for example, via an X2 interface, an Xn interface, or an F1 interface.

The cell provided by the base station 20 may be called a serving cell. The concept of a serving cell includes a PCell (Primary Cell) and an SCell (Secondary Cell). When dual connectivity is provided to the terminal device 40, the PCell and zero or more SCells provided by the MN (Master Node) may be called a Master Cell Group. Examples of dual connectivity include EUTRA-EUTRA Dual Connectivity, EUTRA-NR Dual Connectivity (ENDC), EUTRA-NR Dual Connectivity with 5GC, NR-EUTRA Dual Connectivity (NEDC), and NR-NR Dual Connectivity. Further examples of dual connectivity include NR-6G Dual Connectivity and 6G-NR Dual Connectivity.

The serving cell may include a PSCell (Primary Secondary Cell, or Primary SCG Cell). When dual connectivity is provided to the terminal device 40, the PSCell and zero or more SCells provided by the SN (Secondary Node) may be referred to as a SCG (Secondary Cell Group). Unless special configuration (e.g., PUCCH on SCell) is performed, the physical uplink control channel (PUCCH) is transmitted by the PCell and PSCell but not by the SCell. Radio link failure is detected by the PCell and PSCell but not (does not need to be detected by) the SCell. Thus, the PCell and PSCell are also called SpCells (Special Cells) because they play a special role among the serving cells.

One cell may be associated with one downlink component carrier and one uplink component carrier. The system bandwidth corresponding to one cell may be divided into multiple BWPs (Bandwidth Parts). At this time, one or multiple BWPs may be set in the terminal device 40, and one BWP may be used by the terminal device 40 as an active BWP. Radio resources that the terminal device 40 can use, such as frequency bands, numerology (subcarrier spacing), or slot formats, may differ for each cell, component carrier, or BWP.

<2-3. Configuration of the transmission path control device>
Next, the configuration of the transmission line control device 30 will be described.

The transmission path control device 30 is a control device that dynamically changes the propagation path of radio waves. The transmission path control device 30 is typically a RIS (Reconfigurable Intelligent Surface). In this case, the RIS may be a RIS that operates in cooperation with a base station or other transceivers (referred to as a Cooperative RIS in this embodiment), or a RIS that operates without cooperation with a transceiver (referred to as a Blind RIS in this embodiment). The RIS may also be a RIS that reflects incoming radio waves without amplifying them (referred to as a passive RIS in this embodiment), or a RIS that has the function of amplifying and reflecting incoming radio waves (referred to as an active RIS in this embodiment). The transmission path control device 30 may be a device called a metasurface reflector or a device called a smart repeater. The transmission path control device 30 is not limited to a reflective device, and may be, for example, a transparent device. The description of the transmission path control device 30 that appears in the following explanation can be rephrased as RIS, IRS, IS, metasurface, smart surface, intelligent surface, metamaterial, etc.

The transmission line control device 30 has a structure that reflects or transmits the arriving radio waves. For example, the transmission line control device 30 may have, as a structure, a reflector made up of one or more metasurfaces (metasurface elements) whose permittivity and/or magnetic permeability can be dynamically controlled. The transmission line control device 30 may also have, as a structure, a transmitting plate whose refractive index, etc. of the transmitted radio waves can be controlled. The transmission line control device 30 then controls the reflection characteristics (e.g., reflection direction/reflectance, etc.) or transmission characteristics (e.g., refraction direction/transmittance, etc.) of the structure to reflect/transmit the arriving radio waves at a desired angle.

The transmission line control device 30 may be a device installed on the outer wall of a structure such as a building. By installing the transmission line control device 30 on the outer wall of a structure, even if there is an obstruction between the base station 20 and the terminal device 40, the signal from the base station 20 can be reflected by the transmission line control device 30 provided on the outer wall of the building and reach the terminal device 40. The transmission line control device 30 may also be a device mounted on a device. In this case, the transmission line control device 30 may be a mobile device. The mobile device may be a floating device. For example, the transmission line control device 30 may be mounted on a terminal device such as a smartphone, or on a vehicle such as an automobile, train, or rickshaw, or on an air vehicle (floating body) such as a balloon, airplane, or drone, or on equipment such as a traffic light, sign, or street light, or on home appliances such as a television, game machine, air conditioner, refrigerator, or lighting fixture.

FIG. 7 is a diagram showing an example of the configuration of a transmission line control device 30 according to an embodiment of the present disclosure. The transmission line control device 30 includes a communication unit 31, a storage unit 32, a control unit 33, a sensor unit 34, and a surface unit 35. The transmission line control device 30 does not necessarily have to include all of these components. For example, the transmission line control device 30 does not have to include the sensor unit 34. The transmission line control device 30 may also include a plurality of these components. For example, the transmission line control device 30 may include a plurality of surface units 35. In this case, the plurality of surface units 35 may each face in a different direction. Note that the configuration shown in FIG. 7 is a functional configuration, and the hardware configuration may be different from this. Also, the functions of the transmission line control device 30 may be distributed and implemented in a plurality of physically separated configurations.

The communication unit 31 is a communication interface for communicating with other communication devices (e.g., the management device 10, the base station 20, the terminal device 40, or another transmission path control device 30). The communication unit 31 may be a network interface or a device connection interface. The communication unit 31 may be a LAN (Local Area Network) interface such as a NIC (Network Interface Card), or a Universal Serial Bus (USB) interface configured by a USB host controller or a USB port. The communication unit 31 may be a wired interface or a wireless interface. The communication unit 31 is controlled by the control unit 33.

The memory unit 32 is a storage device capable of reading and writing data, such as a DRAM, SRAM, flash memory, or hard disk.

The control unit 33 is a controller (control device) that controls each part of the transmission line control device 30. The control unit 33 is realized by a processor such as a CPU, MPU, or GPU. For example, the control unit 33 is realized by a processor executing various programs stored in a storage device inside the transmission line control device 30 using a RAM or the like as a working area. The control unit 33 may be realized by an integrated circuit such as an ASIC or FPGA. The control unit 33 may be realized by a GPU. The CPU, MPU, ASIC, FPGA, and GPU can all be considered as controllers. The control unit 33 may be composed of multiple physically separated objects. For example, the control unit 33 may be composed of multiple semiconductor chips.

The control unit 33 includes an acquisition unit 331, a transmission unit 332, a channel estimation control unit 333, a reception unit 334, and an interpolation unit 335. Each block constituting the control unit 33 (acquisition unit 331 to interpolation unit 335) is a functional block indicating a function of the control unit 33. These functional blocks may be software blocks or hardware blocks. For example, each of the above-mentioned functional blocks may be a software module realized by software (including a microprogram), or may be a circuit block on a semiconductor chip (die). Of course, each functional block may be a processor or an integrated circuit. The control unit 33 may be configured in functional units different from the above-mentioned functional blocks. The method of configuring the functional blocks is arbitrary.

The operation of the control unit 33 may be similar to the operation of the control unit 23 of the base station 20 and the control unit 43 of the terminal device 40. The operation of the control unit 33 may be similar to the operation of the control unit 13 of the management device 10. The control unit 33 may be configured to control the surface unit 35 of one or more other transmission path control devices 30.

The sensor unit 34 is a sensor that acquires various information related to wireless communication. For example, the sensor unit 34 is a sensor that acquires information about objects around the device. For example, the sensor unit 34 is a sensor that acquires information about the position, shape, movement, etc. of other objects. The sensor unit 34 may be a sensor for detecting the state of the device itself (for example, the position, moving speed, inclination, vibration, rotation, etc. of the terminal device 40). In addition, the configuration of the sensor unit 34 may be the same as the configuration of the sensor unit 24 provided in the base station 20. For example, the sensor unit 34 may be an RF sensor or a non-RF sensor. Furthermore, the sensor unit 34 may be a sensor system that combines an RF sensor and a non-RF sensor.

The surface portion 35 is a structure that reflects or transmits the arriving radio waves. For example, the surface portion 35 is a reflecting plate composed of a metasurface (metasurface element) whose permittivity and/or permeability can be dynamically controlled. The surface portion 35 may be a transmitting plate that is configured to transmit the arriving radio waves and can control the refractive index of the transmitted radio waves. The transmission line control device 30 is not limited to a plate shape. For example, the transmission line control device 30 may be a sheet shape. The metasurface element is a type of artificial medium (metamaterial) that realizes arbitrary characteristics (e.g., permittivity and permeability) by periodically arranging structures that are small relative to the wavelength. The control unit 33 can control, for example, the amplitude, phase, polarization, or frequency of the arriving radio waves by manipulating the characteristics (e.g., reflection characteristics or transmission characteristics) of the metasurface provided by the surface portion 35. The structure provided by the transmission line control device 30 is not limited to a surface shape. The surface portion 35 that appears in the following description can be rephrased as the metamaterial portion 35, the material portion 35, etc.

FIG. 8 is a diagram showing a configuration example of the surface unit 35 included in the transmission line control device 30. The surface unit 35 includes a plurality of elements 351 capable of changing the characteristics related to the reflection or transmission of the arriving radio wave. The elements 351 are, for example, metasurface elements. In the example of FIG. 8, the surface unit 35 includes m×n elements 351 (elements 351 ₁₁ to 351 _mn ). In addition to a phase shifter 352 that manipulates the reflected wave/transmitted wave, a channel estimation unit 353 is arranged in each of two or more elements 351 among the plurality of elements 351, as shown in FIG. 8, for example. The transmission line control device 30 can switch the circuit connected to the two or more elements 351 from the phase shifter 352 to the channel estimation unit 353. The elements 351 in which the channel estimation unit 353 is arranged may be all of the plurality of elements 351 included in the surface unit 35, or may be a part of the plurality of elements 351. The phase shifter 352 may additionally include a secondary modulation section, an amplifier, and the like.

2-4. Configuration of terminal device
Next, the configuration of the terminal device 40 will be described.

The terminal device 40 is a wireless communication device that performs wireless communication with other wireless communication devices (e.g., a base station 20 or another terminal device 40). Any type of information processing device (computer) can be used for the terminal device 40. For example, the terminal device 40 may be a mobile terminal such as a mobile phone, a smart device (smartphone or tablet), a PDA (Personal Digital Assistant), or a notebook PC. The terminal device 40 may also be an imaging device (e.g., a camcorder) equipped with a communication function. The terminal device 40 may also be a motorcycle or a mobile relay vehicle equipped with a communication device such as an FPU (Field Pickup Unit). The terminal device 40 may also be an M2M (Machine to Machine) device or an IoT (Internet of Things) device. The terminal device 40 may also be a wearable device such as a smart watch.

The terminal device 40 may also be an xR device such as an AR (Augmented Reality) device, a VR (Virtual Reality) device, or an MR (Mixed Reality) device. In this case, the xR device may be a glasses-type device such as AR glasses or MR glasses, or a head-mounted device such as a VR head-mounted display. When the terminal device 40 is an xR device, the terminal device 40 may be a standalone device consisting only of a part worn by the user (e.g., a glasses part). The terminal device 40 may also be a terminal-linked device consisting of a part worn by the user (e.g., a glasses part) and a terminal part linked to the part (e.g., a smart device).

The terminal device 40 may be capable of NOMA communication with the base station 20. The terminal device 40 may be able to use an automatic repeat technique such as HARQ when communicating with the base station 20. The terminal device 40 may be capable of sidelink communication with other terminal devices 40. The terminal device 40 may be able to use an automatic repeat technique such as HARQ when performing sidelink communication. The terminal device 40 may be capable of NOMA communication when performing sidelink communication with other terminal devices 40. The terminal device 40 may be capable of LPWA communication with other wireless communication devices such as the base station 20. The wireless communication used by the terminal device 40 may be wireless communication using millimeter waves. The wireless communication used by the terminal device 40, including sidelink communication, may be wireless communication using radio waves, or wireless communication using infrared rays or visible light, i.e., optical wireless.

The terminal device 40 may be a wireless communication device that can be moved, that is, a mobile device. The terminal device 40 may be a wireless communication device installed in a mobile device, or may be the mobile device itself. The terminal device 40 may be a vehicle that moves on a road, such as an automobile, a bus, a truck, or a motorcycle, or may be a wireless communication device mounted on the vehicle. The mobile device may be a mobile terminal, or may be a mobile device that moves on land (ground in the narrow sense), underground, on water, or underwater. The mobile device may also be a mobile device that moves within the atmosphere, such as an airplane, an airship, a balloon, or a helicopter, or may be a mobile device that moves outside the atmosphere, such as an artificial satellite. The mobile device may be a UAV (Unmanned Aerial Vehicle) such as a drone. The terminal device 40 may also be a wireless communication device mounted on a mobile device.

The terminal device 40 may be capable of connecting to and communicating with multiple base stations 20 or multiple cells at the same time. When one base station 20 supports a communication area through multiple cells (e.g., pCell or sCell), the multiple cells can be bundled together and communication can be performed between the base station 20 and the terminal device 40 using carrier aggregation (CA) technology, dual connectivity (DC) technology, multi-connectivity (MC) technology, or the like. Alternatively, communication can be performed between the terminal device 40 and the multiple base stations 20 through the cells of different base stations 20 using coordinated multi-point transmission and reception (CoMP) technology.

The terminal device 40 may be a relay terminal that relays communication to a remote terminal.

FIG. 9 is a diagram showing the configuration of a terminal device 40 according to this embodiment. The terminal device 40 includes a wireless communication unit 41, a memory unit 42, a control unit 43, and a sensor unit 44. The terminal device 40 does not necessarily have to include all of these components. For example, the terminal device 40 does not have to include the sensor unit 44. Note that the configuration shown in FIG. 9 is a functional configuration, and the hardware configuration may differ from this. Furthermore, the functions of the terminal device 40 may be implemented in a distributed manner across multiple physically separated components.

The wireless communication unit 41 is a signal processing unit for wireless communication with other wireless communication devices (e.g., the base station 20 or other terminal devices 40). The wireless communication unit 41 is controlled by the control unit 43. The wireless communication unit 41 supports one or more wireless access methods. The wireless communication unit 41 may support at least one of NR, LTE, and 6G. In addition to NR, LTE, and 6G, the wireless communication unit 41 may support W-CDMA, cdma2000, etc. The wireless communication unit 41 may support automatic retransmission technology such as HARQ (Hybrid Automatic Repeat reQuest).

The wireless communication unit 41 includes a transmission processing unit 411, a reception processing unit 412, and an antenna 413. The wireless communication unit 41 may include a plurality of transmission processing units 411, reception processing units 412, and antennas 413. When the wireless communication unit 41 supports a plurality of wireless access methods, each unit of the wireless communication unit 41 may be configured separately for each wireless access method. The transmission processing unit 411 and the reception processing unit 412 may be configured separately for LTE, NR, and 6G. The antenna 413 may be configured with a plurality of antenna elements, for example, a plurality of patch antennas. The wireless communication unit 41 may have a beamforming function. For example, the wireless communication unit 41 may have a polarized beamforming function using vertical polarization (V polarization) and horizontal polarization (H polarization) (or a polarized beamforming function using dual polarization in polarization directions of 45 degrees and -45 degrees from the vertical direction).

The memory unit 42 is a readable and writable storage device such as a DRAM, an SRAM, a flash memory, or a hard disk. The memory unit 42 functions as a storage means for the terminal device 40.

The control unit 43 is a controller that controls each part of the terminal device 40. The control unit 43 controls the wireless communication unit so as to perform wireless communication with other wireless communication devices (e.g., the base station 20 or other terminal devices 40). The control unit 43 may be realized by a processor such as a CPU or MPU. In detail, the control unit 23 may be realized by a processor executing various programs stored in a storage device inside the terminal device 40 using a RAM or the like as a working area. The control unit 43 may be realized by an integrated circuit such as an ASIC or FPGA. The control unit 43 may be realized by a GPU. The CPU, MPU, ASIC, FPGA, and GPU can all be considered as controllers. The control unit 43 may be composed of multiple physically separated objects. For example, the control unit 43 may be composed of multiple semiconductor chips.

The control unit 43 includes an acquisition unit 431, a transmission unit 432, and a communication control unit 433. Each block constituting the control unit 43 (acquisition unit 431 to communication control unit 433) is a functional block indicating a function of the control unit 43. These functional blocks may be software blocks or hardware blocks. For example, each of the above-mentioned functional blocks may be a software module realized by software (including a microprogram), or may be a circuit block on a semiconductor chip (die). Of course, each functional block may be a processor or an integrated circuit. The control unit 43 may be configured in functional units different from the above-mentioned functional blocks. The method of configuring the functional blocks is arbitrary.

Note that the operation of each block constituting the control unit 43 may be similar to that of each block provided in the control unit 23 of the base station 20. Also, the operation of the control unit 23 may be similar to that of the control unit 13 of the management device 10.

The sensor unit 44 is a sensor that acquires various information related to wireless communication. For example, the sensor unit 44 is a sensor that acquires information about objects around the device. For example, the sensor unit 44 is a sensor that acquires information about the position, shape, movement, etc. of other objects. The sensor unit 44 may be a sensor for detecting the state of the device itself (for example, the position, moving speed, inclination, vibration, rotation, etc. of the terminal device 40). In addition, the configuration of the sensor unit 44 may be the same as the configuration of the sensor unit 24 provided in the base station 20. For example, the sensor unit 44 may be an RF sensor or a non-RF sensor. Furthermore, the sensor unit 44 may be a sensor system that combines an RF sensor and a non-RF sensor.

<<3. Operation of the communication system>>
The configuration of the communication system 1 has been described above. Next, the operation of the communication system 1 of the present embodiment will be described.

As described above, in a conventional RIS, the communication unit of the RIS performs operations for channel estimation (e.g., sounding operations). However, in this conventional channel estimation method, depending on the RIS (e.g., the shape/size of the RIS), the actual channel conditions and the channel estimation results may differ from the actual channel conditions.

The transmission path control device 30 (e.g., RIS) of this embodiment has a surface section 35 composed of multiple elements 351 that can change the characteristics related to the reflection or transmission of the incoming radio waves. In the transmission path control device 30 of this embodiment, in addition to a phase shifter 352 that manipulates the reflected wave/transmitted wave, a channel estimation section 353 is arranged in each of two or more elements 351 out of the multiple elements 351. The channel estimation section 353 may be arranged in all elements of the multiple elements 351, or may be arranged in some elements of the multiple elements 351. Based on information from these channel estimation sections 353, the transmission path control device 30 obtains information (hereinafter referred to as channel information) related to the results of channel estimation in each of the two or more elements 351. The transmission path control device 30 transmits this channel information to a communication device (e.g., a base station 20 and/or a terminal device 40). The communication device performs processing related to communication between the communication devices based on the channel information.

The above process (hereafter referred to as channel estimation process) will be explained below with reference to the drawings.

<3-1. Channel Estimation Processing>
FIG. 10 is a flowchart showing the channel estimation process of this embodiment.

The communication device (e.g., the base station 20 and/or the terminal device 40) requests capability information related to the channel estimation unit 353 from the transmission path control device 30 (step S101). The transmission path control device 30 transmits the capability information to the communication device (step S102).

Next, the communication device causes the transmission path control device 30 to execute a channel information acquisition operation in order to acquire channel information between the communication device and the transmission path control device 30. Specifically, the communication device transmits a signal (hereinafter referred to as a trigger signal) that triggers a channel estimation operation to the transmission path control device 30 (step S103). The communication device may store information on the channel estimation mode (hereinafter referred to as channel estimation mode information) in this trigger signal. The channel estimation mode information may be composed of one or more pieces of information that specify the mode of channel estimation of the transmission path control device 30. The communication device may determine the information (channel estimation mode) to be stored in this channel estimation mode information based on the capability information acquired in step S102.

The receiver 334 of the transmission path control device 30 receives a trigger signal from the communication device. This trigger signal includes channel estimation mode information. The channel estimation mode information will be described later.

Then, the communication device transmits a signal for channel estimation to the transmission path control device 30 (step S104). Examples of the channel estimation signal include a CSI-RS (Channel State Information-Reference Signal), an SRS (Sounding Reference Signal), or a CSI Report. The communication device may store channel estimation form information in these signals. The communication device may also transmit a new signal that stores the channel estimation form information as the channel estimation signal to be transmitted to the transmission path control device 30.

The channel estimation control unit 333 of the transmission path control device 30 controls the operation of the multiple channel estimation units 353 based on the channel estimation form information. For example, the transmission path control device 30 controls the operation of the multiple channel estimation units 353 so as to achieve a channel estimation form specified by the communication device. For example, the transmission path control device 30 receives a trigger signal and switches the circuit connected to two or more elements 351 in which the channel estimation units 353 are arranged from the phase shifter 352 to the channel estimation unit 353. At this time, the channel estimation control unit 333 may determine the element 351 that switches the connection circuit to the channel estimation unit 353 based on the channel estimation form information. Of course, the channel estimation control unit 333 may control the operation of the channel estimation unit 353 so as to achieve a predetermined channel estimation form. Then, the multiple channel estimation units 353 each perform an operation related to channel estimation based on a channel estimation signal transmitted from the communication device.

The acquisition unit 331 of the transmission path control device 30 acquires information on the results of channel estimation from the multiple channel estimation units 353. Then, the transmission unit 332 of the transmission path control device 30 transmits channel information based on the information on the results of channel estimation to the communication device (step S105). Here, the channel information may be information that integrates the channel estimation results from two or more elements 351.

The communication device acquires channel information from the transmission path control device 30. Then, the communication device performs various controls based on the channel information. For example, the base station 20 performs communication control of the base station 20 and/or the terminal device 40 based on the channel information. For example, the base station 20 determines the communication settings (communication parameters) to be used by the base station 20 and/or the terminal device 40 based on the channel information. The base station 20 and/or the terminal device 40 communicates using the communication settings (communication parameters) determined based on the channel information.

This enables more accurate channel estimation, enabling communication devices (e.g., base station 20 and/or terminal device 40) to perform high-quality communication via transmission path control device 30. As a result, radio wave resources can be used more efficiently.

<3-2. Capability information>
The outline of the transmission line control process has been explained above. Next, the capability information will be explained.

As described above, the transmission path control device 30 transmits capability information to the communication device (step S102). The capability information is capability information related to channel estimation by the transmission path control device 30 (e.g., RIS). This capability information is signaled in advance between the communication device and the transmission path control device 30 before the channel estimation operation. The communication device (e.g., base station 20 and/or terminal device 40) determines the element 351 (e.g., metasurface element) to be used for channel estimation according to the accuracy of the beam used during communication using the RIS and the form of channel estimation.

Here, it is assumed that the transmission line control device 30 (or the surface unit 35 provided in the transmission line control device 30) is the RIS. In this case, the capability information may include at least one of the pieces of information shown in (A1) to (A9) below. Of course, the information included in the capability information is not limited to the information shown in (A1) to (A9) below. Note that the description of RIS shown below can be replaced with the transmission line control device 30 or the surface unit 35.

(A1) Information on the size of the RIS The information on the size of the RIS is information that specifically indicates the size of the RIS (for example, the transmission line control device 30, or the surface unit 35 included in the transmission line control device 30). For example, the information on the size of the RIS may be at least one of the pieces of information shown in the following (A1-1) to (A1-3).
(A1-1) Information indicating the size of the RIS in numerical form. (A1-2) Information indicating to which size category the size of the RIS belongs, as defined in advance by standardization standards, etc. (A1-3) Information on the effective area of the RIS with respect to a communication device (e.g., a base station 20 and/or a terminal device 40).

(A2) Information on the size of the element 351 The information on the size of the element 351 is information that specifically indicates the size of the element 351 (e.g., metasurface element) included in the RIS. For example, the information on the size of the RIS may be at least one of the pieces of information shown in (A2-1) to (A2-2) below.
(A2-1) Information indicating, in numerical form, the size of the element 351. (A2-2) Information indicating to which size category the size of the element 351 belongs, which is predefined in a standardization specification or the like.

(A3) Information on the arrangement of the elements 351 The information on the arrangement of the elements 351 is information indicating the arrangement of the elements 351 (e.g., metasurface elements). The information on the arrangement of the elements 351 includes, for example, at least one of information indicating the arrangement interval of the elements 351 and information indicating the area ratio of the elements 351 to the area of the RIS.

(A4) Information on the Function of Each Element 351 The information on the function of each element 351 is information on the function for controlling the reflected wave/transmitted wave for each element 351 (e.g., metasurface element). The function for controlling the reflected wave/transmitted wave includes, for example, at least one of the phase shifter 352, the amplifier, the secondary modulation unit, and the channel estimation unit 353.

(A5) Information Regarding Control Precision of Element 351 Information regarding the control precision of the element 351 is, for example, information indicating the controllable granularity for each of the above-mentioned functions (functions of each element 351).

(A6) Information on the form of channel estimation The information on the form of channel estimation is information indicating which form the RIS can support among a plurality of forms of channel estimation including the operation of this embodiment (for example, forms of channel estimation defined in advance by a standardization standard, etc.). The information on the form of channel estimation may include at least one of information on the mapping pattern of the element 351 (for example, metasurface element) having the channel estimation unit 353, and information on whether each element 351 (for example, metasurface element) has the channel estimation unit 353.

(A7) Identification information for each element 351 The identification information for each element 351 is information (e.g., ID information) used to identify a target element 351 from multiple elements 351 when a communication device specifies the operation of the element 351 (e.g., metasurface element). Note that the capability information may include, in addition to the identification information for each element 351, at least one of information on the mapping pattern of the element 351 (e.g., metasurface element) having the channel estimation unit 353, and information on whether each element 351 (e.g., metasurface element) has the channel estimation unit 353, as information on the element 351.

(A8) Information on the format of the channel estimation result The information on the format of the channel estimation result is information indicating which of a plurality of feedback formats of the channel estimation result the RIS (for example, the transmission path control device 30) supports.

(A9) RIS Identification Information The RIS identification information is information (e.g., ID information) that enables a communication device to identify the RIS.

<3-3. Channel Estimation Type Information>
Next, the channel estimation mode information will be described.

As described above, the communication device transmits channel estimation mode information to the transmission path control device 30 (e.g., RIS). In the above-mentioned channel estimation process, the channel estimation mode information is stored in a trigger signal and transmitted (step S103). The channel estimation mode information is composed of, for example, one or more pieces of information that specify the mode of channel estimation of the transmission path control device 30.

Here, it is assumed that the transmission path control device 30 (or the surface unit 35 included in the transmission path control device 30) is a RIS. In this case, the channel estimation mode information may include at least one of the pieces of information shown in (B1) to (B4) below. Of course, the information included in the channel estimation mode information is not limited to the information shown in (B1) to (B4) below. The operation of the communication system 1 in each of the cases (B1) to (B4) will be described in detail in Examples 1 to 4 below. Note that the description of RIS shown below can be replaced with the transmission path control device 30 or the surface unit 35.

(B1) A form in which only channel estimation at a single frequency is performed. (B2) A form in which different frequency bands are simultaneously channel-estimated. (B3) A form in which channels are simultaneously estimated between the RIS and the base station 20 and between the RIS and the terminal device 40. (B4) A form in which other signals are reflected/transmitted at the same time as channel estimation.

The channel estimation form information may be information that specifically indicates a form of channel estimation defined in a standard specification or the like. The channel estimation form information may also be information that specifies the allocation of operations related to channel estimation for each element 351 (e.g., metasurface element). This also allows the communication device to indirectly specify the form of channel estimation.

The information specifying the allocation of operations related to channel estimation may be information specifying an element 351 to be used during channel estimation (hereinafter referred to as element specification information). The element specification information is information for specifying which of the multiple elements 351 the RIS is to use as its channel estimation unit 353.

The element designation information may include at least one of the pieces of information shown in (C1) to (C9) below. Of course, the information included in the element designation information is not limited to the pieces of information shown in (C1) to (C9) below. The description of the RIS shown below can be replaced with the transmission path control device 30 or the surface unit 35.

(C1) Mapping pattern designation information of the element 351 used for channel estimation (e.g., information on a mapping pattern selected from a plurality of mapping patterns specifically defined in a standardization specification, etc.)
(C2) Mapping pattern designation information determined based on capability information related to channel estimation of the RIS (e.g., information on a mapping pattern selected from a plurality of mapping patterns predefined between the RIS and the communication device)
(C3) Mapping pattern designation information determined based on implementation (C4) Designation information for each element 351 as to whether to perform channel estimation (C5) Designation information for each element 351 as to whether to use a predetermined function (e.g., a band-limiting filter) (C6) Information on the number of elements to be used for channel estimation per unit area (C7) Information on the number of elements to be used for channel estimation out of the total number of elements 351 (C8) Information on the ratio of the number of elements to be used for channel estimation out of the total number of elements 351 (C9) Information designating whether channel estimation is to be performed by the channel estimation unit 353 or the communication unit 31 (e.g., information designating whether channel estimation is to be performed on an element-by-element basis or on a RIS-by-RIS basis)

In addition, when the communication device specifies a mapping pattern to be used by the RIS from among multiple mapping patterns predefined between the RIS and the communication device, information on the mapping pattern is signaled in advance between the RIS and the communication device (e.g., between the RIS and the base station 20 and/or between the RIS and the terminal device 40).

<3-4. Channel information>
Next, the channel information will be described.

The transmission path control device 30 (e.g., RIS) feeds back channel information based on information on the result of channel estimation to the communication device (step S105). Here, the information on the result of channel estimation may be information on an element 351 (e.g., metasurface element) basis. Also, the information on the result of channel estimation may be information in a format that allows the correspondence between the element 351 and the result of channel estimation to be identified. The transmission path control device 30 may feed back the result of channel estimation to the communication device (e.g., base station 20 and/or terminal device 40) based on the element designation information.

When only a specific element 351 has a channel estimation unit 353, the transmission path control device 30 may estimate and interpolate the channel estimation results of the other elements 351 based on the channel estimation result of the specific element 351. For example, the interpolation unit 335 of the transmission path control device 30 may interpolate the channel estimation results for elements 351 among the multiple elements 351 for which channel estimation results have not been obtained based on the channel estimation results of elements 351 for which channel estimation results have been obtained. Then, the transmission unit 332 of the transmission path control device 30 may transmit channel information based on the multiple channel estimation results including the interpolated channel estimation result to the communication device. The transmission path control device 30 may perform this interpolation process only when specified by the communication device. This allows the transmission path control device 30 to improve the accuracy of channel estimation.

The transmission path control device 30 may also transmit information that integrates the channel estimation results of the multiple elements 351 to the communication device as channel information. The transmission path control device 30 may feed back this integrated information as the channel estimation result of the representative element 351. This allows the transmission path control device 30 to reduce the amount of feedback information.

The transmission path control device 30 may also transmit information on the difference between the channel estimation result of a specific element 351 and the channel estimation results of other elements 351 as channel information to the communication device. For example, the transmission path control device 30 may transmit information indicating the channel estimation result of one element 351 of the multiple elements 351 and information on the channel estimation results of other elements 351 of the multiple elements 351 expressed as the difference between the channel estimation result of the one element 351 as channel information to the communication device. This also enables the transmission path control device 30 to reduce the amount of feedback information.

<3-5. How to use channel information>
Next, a method for using the channel information obtained by the above-described channel estimation process will be described.

The communication device obtains channel information from the transmission path control device 30 (e.g., RIS). Then, the communication device (e.g., base station 20 and/or terminal device 40) performs various controls based on the channel information. For example, the communication device uses the obtained channel information to determine the control method for each element 351, the form of the beam it will transmit, and the antenna port to be used. Note that if the communication device does not obtain channel estimation results for all elements 351 (e.g., if only a specific element 351 of the transmission path control device 30 has a channel estimation unit 353), the communication device may use the channel estimation result of a specific element 351 to interpolate channel information for the other elements 351.

<<4. Example>>
The operation of the communication system 1 has been described above. Next, an embodiment of the above-mentioned channel estimation process will be described.

In the embodiment described below, a communication environment is assumed in which a base station 20 and a terminal device 40 communicate with each other. In this communication environment, one or more RISs are installed as a transmission path control device 30. In the following explanation, these multiple RISs may be referred to as RIS#1 to RIS#N, where N is any integer. Note that the RIS that appears in the following explanation can be replaced with a transmission path control device 30 other than a RIS.

As described above, the RIS performs processing related to channel estimation in this embodiment based on channel estimation form information from the communication device (base station 20 and/or terminal device 40). The form of channel estimation of this RIS can be divided into the forms shown in (B1) to (B4) below, for example.

(B1) A form in which only channel estimation at a single frequency is performed. (B2) A form in which different frequency bands are simultaneously channel-estimated. (B3) A form in which channels are simultaneously estimated between the RIS and the base station 20 and between the RIS and the terminal device 40. (B4) A form in which other signals are reflected/transmitted at the same time as channel estimation.

Below, examples of (B1) to (B4) are explained.

<4-1. Example 1>
In the first embodiment, a case will be described in which the RIS performs channel estimation only at a single frequency. The first embodiment is an example of the form shown in (B1) above.

FIG. 11 is a sequence diagram showing the channel estimation process according to the first embodiment. The channel estimation process according to the first embodiment will be described below with reference to FIG. 11.

The base station 20 or the terminal device 40 requests capability information related to RIS channel estimation from the RIS (step S201). The RIS transmits the capability information to the base station 20 or the terminal device 40 (step S202).

The acquisition unit 231 of the base station 20 or the acquisition unit 431 of the terminal device 40 acquires capability information from the RIS. The base station 20 or the terminal device 40 transmits a trigger signal to the RIS to trigger a channel estimation operation (step S203). The base station 20 or the terminal device 40 stores channel estimation form information in this trigger signal. The base station 20 or the terminal device 40 may determine the information (channel estimation form) to be stored in this channel estimation form information based on the capability information acquired in step S202.

The RIS receives a trigger signal from the base station 20 or the terminal device 40. This trigger signal includes channel estimation mode information. In the first embodiment, it is assumed that the mode shown in (B1) above is specified as the channel estimation mode.

The transmitting unit 232 of the base station 20 or the transmitting unit 432 of the terminal device 40 transmits a signal for channel estimation to the RIS (step S204). Examples of the channel estimation signal include a CSI-RS (Channel State Information-Reference Signal), an SRS (Sounding Reference Signal), or a CSI Report. The communication device may store channel estimation form information in these signals. The communication device may also use a new signal that stores channel estimation form information as the channel estimation signal to be transmitted to the RIS.

The RIS controls the operation of the multiple channel estimation units 353 so that the channel estimation mode specified by the communication device is achieved. For example, upon receiving a trigger signal, the RIS switches the circuit connected to the two or more elements 351 in which the channel estimation units 353 are arranged from the phase shifter 352 to the channel estimation unit 353. At this time, the channel estimation control unit 333 may determine the element 351 that switches the connection circuit to the channel estimation unit 353 based on the channel estimation mode information. Then, each of the multiple channel estimation units 353 performs an operation related to channel estimation based on the channel estimation signal transmitted from the communication device.

FIG. 12 is a diagram for explaining an example of the operation of the RIS. Specifically, FIG. 12 is a diagram for explaining an example of the operation of the RIS in the case where elements 351 that perform channel estimation and elements 351 that do not perform channel estimation are arranged alternately. In the example of FIG. 12, the elements 351 that do not perform channel estimation are positioned so that they are sandwiched on all four sides by the elements 351 that perform channel estimation. The elements 351 that perform channel estimation are, for example, elements 351 connected to a channel estimation unit 353. The elements 351 that do not perform channel estimation are elements 351 connected to a phase shifter 352. The elements 351 that do not perform channel estimation may be elements 351 in which a channel estimation unit 353 is not arranged, as a connectable circuit (switchable circuit).

The channel estimation unit 353 of an element 351 that does not perform channel estimation may calculate its own channel estimation result based on the channel estimation results of surrounding elements 351 that perform channel estimation. In this case, the channel estimation unit 353 may take the average of the channel estimation results of the surrounding elements 351 as its own channel estimation result. In addition, the channel estimation unit 353 may use the channel estimation result of a specific element 351 as its own channel estimation result as it is. Of course, the channel estimation unit 353 may calculate the channel estimation result based on a specific calculation formula.

The channel estimation control unit 333 of the RIS may calculate the channel estimation result of the element 351 that does not perform channel estimation based on the channel estimation results of the elements 351 located around the element 351 that does not perform channel estimation. In this case, the channel estimation control unit 333 may take the average of the channel estimation results of the elements 351 located around the element 351 that does not perform channel estimation as the channel estimation result of the element 351 that does not perform channel estimation. The channel estimation control unit 333 may also use the channel estimation result of a specific element 351 as the channel estimation result of the element 351 that does not perform channel estimation. Of course, the channel estimation unit 353 may calculate the channel estimation result based on a specific calculation formula.

Returning to FIG. 11, the RIS acquires channel estimation results of the multiple elements 351. The RIS then generates channel information based on the acquired channel estimation results. Here, the channel information may be information that integrates the channel estimation results of each of the multiple elements 351. The RIS then transmits the channel information to the base station 20 or the terminal device 40 (step S205).

The base station 20 or the terminal device 40 acquires channel information from the RIS. Then, the base station 20 or the terminal device 40 performs various processes related to communication based on the channel information.

<4-2. Example 2>
In the second embodiment, a case where the RIS simultaneously estimates channels of different frequency bands will be described. The second embodiment is an example of the form shown in (B2) above. In the second embodiment, the RIS includes a surface portion 35 (a plurality of elements 351) capable of simultaneously reflecting/transmitting radio waves of a plurality of frequency bands.

<4-2-1. Sequence example>
13 is a sequence diagram illustrating a channel estimation process according to the second embodiment. Hereinafter, the channel estimation process according to the second embodiment will be described with reference to FIG.

The base station 20 or the terminal device 40 requests capability information related to RIS channel estimation from the RIS (step S301). The RIS transmits the capability information to the base station 20 or the terminal device 40 (step S302).

The acquisition unit 231 of the base station 20 or the acquisition unit 431 of the terminal device 40 acquires capability information from the RIS. The base station 20 or the terminal device 40 transmits a trigger signal to the RIS to trigger a channel estimation operation (step S303). The base station 20 or the terminal device 40 stores channel estimation form information in this trigger signal. The base station 20 or the terminal device 40 may determine the information (channel estimation form) to be stored in this channel estimation form information based on the capability information acquired in step S302.

The RIS receives a trigger signal from the base station 20 or the terminal device 40. This trigger signal includes channel estimation mode information. In the second embodiment, it is assumed that the mode shown in (B2) above is specified as the channel estimation mode. The RIS controls the operation of the multiple channel estimation units 353 so as to achieve the channel estimation mode specified by the communication device. For example, upon receiving the trigger signal, the RIS switches the circuit connected to the element 351 in which the channel estimation unit 353 is located based on the channel estimation mode information.

The transmitter 232 of the base station 20 or the transmitter 432 of the terminal device 40 transmits a channel estimation signal for frequency band #1 to the RIS (step S304). Each of the multiple channel estimation units 353 included in the RIS performs operations related to channel estimation based on the channel estimation signal for frequency band #1. The RIS acquires channel estimation results of the multiple elements 351. The RIS then generates channel information for frequency band #1 based on the acquired channel estimation results. The RIS then transmits the channel information for frequency band #1 to the base station 20 or the terminal device 40 (step S305).

The transmitter 232 of the base station 20 or the transmitter 432 of the terminal device 40 transmits a channel estimation signal for frequency band #2 to the RIS (step S306). Each of the multiple channel estimation units 353 included in the RIS performs operations related to channel estimation based on the channel estimation signal for frequency band #2. The RIS acquires channel estimation results of the multiple elements 351. The RIS then generates channel information for frequency band #2 based on the acquired channel estimation results. The RIS then transmits the channel information for frequency band #2 to the base station 20 or the terminal device 40 (step S307).

The frequency bands related to the channel estimation process are not limited to frequency band #1 and frequency band #2. The base station 20 or the terminal device 40 may transmit channel estimation signals related to more than two frequency bands. The RIS may also perform operations related to channel estimation related to more than two frequency bands.

The RIS may feed back channel estimation results of multiple frequency bands to the base station 20 or the terminal device 40 as one channel information (or one signal). If there is similarity in the channels, the RIS may feed back, as channel information, to the base station 20 or the terminal device 40, first information, which is the channel estimation result of one frequency band, and second information, which is the channel estimation result of another frequency band and is difference information between the first information and the first information.

The base station 20 or the terminal device 40 acquires channel information from the RIS. Then, the base station 20 or the terminal device 40 performs various processes related to communication based on the channel information.

<4-2-2. Example of RIS configuration>
Fig. 14 is a diagram showing a configuration example of a RIS (transmission path control device 30) according to the second embodiment. When frequency bands for which channels are simultaneously estimated in the RIS are close to each other, one or more band-limiting filters (frequency filters #1 to #N in the example of Fig. 14) may be provided before the phase shifter 352 and the channel estimation unit 353. By introducing the band-limiting filters, it is possible to prevent each other's channel estimation signals from affecting other frequency bands as interference.

<4-2-3. Example of RIS operation>
An example of the operation of the RIS when simultaneously estimating channels in different frequency bands is shown below. Figures 15 to 17 are diagrams for explaining an example of the operation of the RIS when simultaneously estimating channels in two different frequency bands (frequency band #1 and frequency band #2).

(Operation example 1)
FIG. 15 is a diagram showing an example of the operation of the RIS in the case where an element 351 performing channel estimation of frequency band #1 and an element 351 performing channel estimation of frequency band #2 are alternately arranged. In the example of FIG. 15, an element 351 not performing channel estimation of frequency band #1 is located in such a manner that it is sandwiched between elements 351 performing channel estimation of frequency band #1 on all four sides. The channel estimation unit 353 of the element 351 not performing channel estimation of frequency band #1 may calculate its own channel estimation result based on the channel estimation result of the element 351 performing channel estimation of frequency band #1 located in the periphery. At this time, the channel estimation unit 353 may use the average of the channel estimation results of the elements 351 located in the periphery as its own channel estimation result. In addition, the channel estimation unit 353 may use the channel estimation result of a specific element 351 as its own channel estimation result as it is. Of course, the channel estimation unit 353 may calculate the channel estimation result based on a specific calculation formula. The channel estimation result may be interpolated by the channel estimation control unit 333 instead of the channel estimation unit 353. Moreover, the interpolation of the channel estimation result may be performed by the base station 20 and/or the terminal device 40. The channel estimation result of the frequency band #2 can also be obtained by the same process.

(Operation example 2)
Fig. 16 is a diagram showing an example of the operation of the RIS when the element 351 performing channel estimation of frequency band #1 and the element 351 performing channel estimation of frequency band #2 are arranged in half of the RIS. In the example of Fig. 16, the element 351 performing channel estimation of frequency band #1 and the element 351 performing channel estimation of frequency band #2 are arranged in the left and right halves of the RIS, but they may be arranged in the upper and lower halves, or may be arranged in diagonal halves. In the example of Fig. 16, the RIS may generate channel information related to frequency band #1 based on the channel estimation result of the element 351 performing channel estimation of frequency band #1. In addition, the RIS may generate channel information related to frequency band #2 based on the channel estimation result of the element 351 performing channel estimation of frequency band #2.

(Operation example 3)
FIG. 17 is a diagram showing an example of the operation of the RIS in the case where the element 351 performing channel estimation of the frequency band #1 and the element 351 performing channel estimation of the frequency band #2 are arranged at different ratios. The RIS may change this ratio according to a predetermined condition. For example, the RIS may change this ratio based on the ratio of the number of elements 351 used for reflection/transmission for each frequency band and/or the required accuracy of channel estimation. The RIS may obtain information on the conditions for determining the ratio (or information on the ratio itself) from the base station 20 and/or the terminal device 40. This information may be included in the channel estimation form information. In the case of the example of FIG. 17, the RIS may generate channel information on the frequency band #1 based on the channel estimation result of the element 351 performing channel estimation of the frequency band #1. The RIS may also generate channel information on the frequency band #2 based on the channel estimation result of the element 351 performing channel estimation of the frequency band #2.

In the above three examples, channel estimation is performed in all elements 351, but the multiple elements 351 included in the RIS may include elements 351 that do not perform channel estimation.

<4-3. Example 3>
In the third embodiment, a case will be described in which the RIS simultaneously estimates the channel between the RIS and the base station 20 and between the RIS and the terminal device 40. The third embodiment is an example of the form shown in (B3) above.

FIG. 18 is a sequence diagram showing the channel estimation process according to the third embodiment. The channel estimation process according to the third embodiment will be described below with reference to FIG. 18.

The base station 20 requests capability information related to RIS channel estimation from the RIS (step S401). The RIS transmits the capability information to the base station 20 (step S402). In the example of FIG. 18, the base station 20 requests the RIS to transmit capability information, but the terminal device 40 may also request the RIS to transmit capability information. In this case, the RIS may transmit the capability information to the terminal device 40.

The acquisition unit 231 of the base station 20 or the acquisition unit 431 of the terminal device 40 acquires capability information from the RIS. The base station 20 or the terminal device 40 transmits a trigger signal to the RIS to trigger a channel estimation operation (step S403). The acquisition unit 431 of the terminal device 40 may acquire capability information from the RIS. Then, the terminal device 40 may transmit a trigger signal to the RIS. The base station 20 or the terminal device 40 stores channel estimation form information in this trigger signal. The base station 20 or the terminal device 40 may determine the information (channel estimation form) to be stored in this channel estimation form information based on the capability information acquired in step S402.

The RIS receives a trigger signal from the base station 20 or the terminal device 40. This trigger signal includes channel estimation mode information. In the third embodiment, it is assumed that the mode shown in (B3) above is specified as the channel estimation mode. The RIS controls the operation of the multiple channel estimation units 353 so as to achieve the channel estimation mode specified by the communication device. For example, upon receiving the trigger signal, the RIS switches the circuit connected to the element 351 in which the channel estimation unit 353 is located based on the channel estimation mode information.

The transmitting unit 232 of the base station 20 transmits a channel estimation signal to the RIS (step S404a). The transmitting unit 432 of the terminal device 40 transmits a channel estimation signal to the RIS (step S404b). At this time, the base station 20 and the terminal device 40 transmit the channel estimation signal (e.g., CSI-RS or SRS) in a form that allows the RIS side to distinguish whether it is a channel estimation signal between the RIS and the base station 20 or a channel estimation signal between the RIS and the terminal device 40.

For example, the base station 20 may use half of the radio resources used for the CSI-RS as a signal for channel estimation between the RIS and the base station 20, and the terminal device 40 may use the remaining half as a signal for channel estimation between the RIS and the terminal device 40. In this case, the radio resources for channel estimation between the RIS and the base station 20 and the radio resources for channel estimation between the RIS and the terminal device 40 may be allocated in a manner that is orthogonal in time, frequency, or space. In this case, the allocation of the radio resources does not necessarily have to be 50/50. The radio resources may be allocated based on the control accuracy of the required elements 351 and/or the proportion of the RIS elements 351 used in the uplink and downlink, respectively.

The multiple channel estimation units 353 included in the RIS each perform operations related to channel estimation based on the channel estimation signal between the RIS and the base station 20. The RIS acquires the channel estimation results of the multiple elements 351. The RIS then generates channel information between the RIS and the base station 20 based on the acquired channel estimation results. The RIS then transmits the channel information between the RIS and the base station 20 to the base station 20 (step S405a).

The multiple channel estimation units 353 included in the RIS each perform operations related to channel estimation based on the channel estimation signal between the RIS and the terminal device 40. The RIS acquires channel estimation results from the multiple elements 351. The RIS then generates channel information between the RIS and the terminal device 40 based on the acquired channel estimation results. The RIS then transmits the channel information between the RIS and the terminal device 40 to the terminal device 40 (step S405b).

The base station 20 and the terminal device 40 acquire channel information from the RIS. Then, the base station 20 and the terminal device 40 perform various communication-related processes based on the channel information.

The RIS (transmission path control device 30) according to the third embodiment may also include one or more band-limiting filters before the phase shifter 352 and the channel estimation unit 353, similar to the RIS according to the second embodiment (e.g., the RIS shown in FIG. 14).

In addition, when channel estimation between the RIS and the base station 20 and channel estimation between the RIS and the terminal device 40 are performed simultaneously, some of the multiple elements 351 may be assigned as elements used for channel estimation between the RIS and the base station 20, and the remaining elements may be assigned as elements used for channel estimation between the RIS and the terminal device 40.

(Configuration Example 1)
For example, the element 351 performing channel estimation between the RIS and the base station 20 and the element 351 performing channel estimation between the RIS and the terminal device 40 may be arranged alternately. For example, the configuration of the RIS of the third embodiment may be a configuration in which the "element that does not perform channel estimation of frequency band #1" is replaced with the "element that performs channel estimation between the RIS and the base station 20" and the "element that does not perform channel estimation of frequency band #2" is replaced with the "element that performs channel estimation between the RIS and the terminal device 40" shown in FIG. 15 described above. In this case, the element 351 that does not perform channel estimation between the RIS and the base station 20 is located in such a manner that it is sandwiched on all four sides between the metasurface elements that perform channel estimation between the RIS and the base station 20. The channel estimation unit 353 of the element 351 that does not perform channel estimation of the frequency band #1 may calculate its own channel estimation result based on the channel estimation result of the element 351 that performs channel estimation between the RIS and the base station 20 located in the periphery. At this time, the channel estimation unit 353 may take the average of the channel estimation results of the elements 351 located in the periphery as its own channel estimation result. Furthermore, the channel estimation unit 353 may use the channel estimation result of a specific element 351 as its own channel estimation result as it is. Of course, the channel estimation unit 353 may calculate the channel estimation result based on a specific calculation formula. The channel estimation result may be interpolated by the channel estimation control unit 333, not by the channel estimation unit 353. The channel estimation result may be interpolated by the base station 20 and/or the terminal device 40. The channel estimation result of the RIS-terminal device 40 can also be obtained by a similar process.

(Configuration Example 2)
For example, the element 351 performing channel estimation between the RIS and the base station 20 and the element 351 performing channel estimation between the RIS and the terminal device 40 may each be arranged in half of the RIS. For example, the configuration of the RIS in the third embodiment may be a configuration in which the "element that does not perform channel estimation of frequency band #1" shown in the above-mentioned FIG. 16 is replaced with the "element that performs channel estimation between the RIS and the base station 20" and the "element that does not perform channel estimation of frequency band #2" is replaced with the "element that performs channel estimation between the RIS and the terminal device 40". The element 351 performing channel estimation between the RIS and the base station 20 and the element 351 performing channel estimation between the RIS and the terminal device 40 may be arranged in the left and right halves of the RIS, or in the top and bottom halves, or in the diagonal halves. In this case, the RIS may generate channel information regarding the RIS and the base station 20 based on the channel estimation result of the element 351 performing channel estimation between the RIS and the base station 20, for example. Also, the RIS may generate channel information regarding the RIS-terminal device 40 relationship based on the channel estimation result of an element 351 that performs channel estimation between the RIS and the terminal device 40, for example.

(Configuration Example 3)
For example, the element 351 performing channel estimation between the RIS and the base station 20 and the element 351 performing channel estimation between the RIS and the terminal device 40 may be arranged at different ratios. For example, the configuration of the RIS of the third embodiment may be a configuration in which the "element that does not perform channel estimation of frequency band #1" shown in the above-mentioned FIG. 17 is replaced with the "element that performs channel estimation between the RIS and the base station 20" and the "element that does not perform channel estimation of frequency band #2" is replaced with the "element that performs channel estimation between the RIS and the terminal device 40". Alternatively, the configuration of the RIS of the third embodiment may be a configuration in which the "element that does not perform channel estimation of frequency band #1" shown in the above-mentioned FIG. 17 is replaced with the "element that performs channel estimation between the RIS and the terminal device 40" and the "element that does not perform channel estimation of frequency band #2" is replaced with the "element that performs channel estimation between the RIS and the base station 20". The RIS may change this ratio according to a predetermined condition. For example, the RIS may change this ratio based on the ratio of the number of elements 351 used for reflection/transmission for each link (e.g., for each uplink/downlink) and/or the required accuracy of channel estimation. The RIS may obtain information on the conditions for determining the ratio (or information on the ratio itself) from the base station 20 and/or the terminal device 40. This information may be included in the channel estimation form information. In the case of the example of FIG. 17, the RIS may generate channel information regarding the RIS-base station 20 based on the channel estimation result of the element 351 that performs channel estimation between the RIS and the base station 20. The RIS may also generate channel information regarding the RIS-terminal device 40 based on the channel estimation result of the element 351 that performs channel estimation between the RIS and the terminal device 40.

In the above three examples, channel estimation is performed in all elements 351, but the multiple elements 351 included in the RIS may include elements 351 that do not perform channel estimation.

<4-4. Example 4>
In the fourth embodiment, a case will be described in which the RIS reflects/transmits other signals at the same time as channel estimation. The fourth embodiment is an example of the form shown in (B4) above.

FIG. 19 is a sequence diagram showing the channel estimation process according to the fourth embodiment. The channel estimation process according to the fourth embodiment will be described below with reference to FIG. 19.

The base station 20 requests capability information related to RIS channel estimation from the RIS (step S501). The RIS transmits the capability information to the base station 20 (step S502). In the example of FIG. 19, the base station 20 requests the RIS to transmit capability information, but the terminal device 40 may also request the RIS to transmit capability information. In this case, the RIS may transmit the capability information to the terminal device 40.

The acquisition unit 231 of the base station 20 or the acquisition unit 431 of the terminal device 40 acquires capability information from the RIS. The base station 20 or the terminal device 40 transmits a trigger signal to the RIS to trigger a channel estimation operation (step S503). The acquisition unit 431 of the terminal device 40 may acquire capability information from the RIS. Then, the terminal device 40 may transmit a trigger signal to the RIS. The base station 20 or the terminal device 40 stores channel estimation form information in this trigger signal. The base station 20 or the terminal device 40 may determine the information (channel estimation form) to be stored in this channel estimation form information based on the capability information acquired in step S502.

The RIS receives a trigger signal from the base station 20 or the terminal device 40. This trigger signal includes channel estimation mode information. In the third embodiment, it is assumed that the mode shown in (B4) above is specified as the channel estimation mode. The RIS controls the operation of the multiple channel estimation units 353 so as to achieve the channel estimation mode specified by the communication device. For example, upon receiving the trigger signal, the RIS switches the circuit connected to the element 351 in which the channel estimation unit 353 is located based on the channel estimation mode information.

The trigger signal (or channel estimation form information) may include information regarding the beam pattern of the transmission signal of the terminal device 40. The RIS switches the circuit connected to a specified element 351 among the multiple elements 351 to a specified circuit (e.g., a specified frequency filter and/or a channel estimation unit 353/phase shifter 352) based on the information regarding the beam pattern and/or the channel estimation form information. At this time, the information regarding the beam pattern may be information that specifically specifies the operation of the element 351, or may be information that specifies the direction and/or focus of the beam to be formed.

The transmitting unit 232 of the base station 20 transmits a channel estimation signal to the RIS (step S504). The transmitting unit 432 of the terminal device 40 may transmit a channel estimation signal to the RIS. The transmitting unit 432 of the terminal device 40 may also transmit an uplink signal to the RIS (step S505a). The transmitting unit 232 of the base station 20 may also transmit a downlink signal to the RIS.

The RIS operates the elements 351 to form the desired beam pattern. This causes a reflected/transmitted signal to be transmitted to the base station 20 (step S505b). When the base station 20 transmits a downlink signal to the RIS, the reflected/transmitted signal is transmitted to the terminal device 40.

The multiple channel estimation units 353 included in the RIS each perform operations related to channel estimation based on the channel estimation signal. The RIS acquires the channel estimation results of the multiple elements 351. The RIS then generates channel information based on the acquired channel estimation results. The RIS then transmits the channel information to the base station 20 (step S506).

The base station 20 acquires channel information from the RIS. Then, the base station 20 performs various processes related to communication based on the channel information. Note that the terminal device 40 may acquire channel information from the RIS. In this case, the terminal device 40 may perform various processes related to communication based on the channel information.

The RIS (transmission path control device 30) according to the fourth embodiment may also include one or more band-limiting filters before the phase shifter 352 and the channel estimation unit 353, similar to the RIS according to the second embodiment (e.g., the RIS shown in FIG. 14).

In addition, when the RIS reflects/transmits other signals at the same time as estimating the channel, some of the multiple elements 351 may be assigned as elements used for channel estimation, and the rest as elements used for reflection/transmission.

(Configuration Example 1)
For example, the element 351 that performs channel estimation and the element 351 that is used for reflection/transmission may be arranged alternately. For example, the configuration of the RIS of the fourth embodiment may be a configuration in which the "element that does not perform channel estimation of frequency band #1" shown in the above-mentioned FIG. 15 is replaced with the "element that performs channel estimation" and the "element that does not perform channel estimation of frequency band #2" is replaced with the "element that is used for reflection/transmission". In this case, the element 351 that does not perform channel estimation is located in such a manner that it is sandwiched between the metasurface elements that perform channel estimation on all four sides. The channel estimation unit 353 of the element 351 that does not perform channel estimation may calculate its own channel estimation result based on the channel estimation result of the element 351 that performs channel estimation located in the periphery. At this time, the channel estimation unit 353 may use the average of the channel estimation results of the elements 351 located in the periphery as its own channel estimation result. In addition, the channel estimation unit 353 may use the channel estimation result of a specific element 351 as its own channel estimation result. Of course, the channel estimation unit 353 may calculate the channel estimation result based on a specific calculation formula. The channel estimation result may be interpolated by the channel estimation control unit 333, instead of the channel estimation unit 353. The channel estimation result may be interpolated by the base station 20 and/or the terminal device 40.

(Configuration Example 2)
For example, the element 351 performing channel estimation and the element 351 used for reflection/transmission may each be arranged in half of the RIS. For example, the configuration of the RIS of the fourth embodiment may be a configuration in which the "element not performing channel estimation of frequency band #1" shown in the above-mentioned FIG. 16 is replaced with the "element performing channel estimation" and the "element not performing channel estimation of frequency band #2" is replaced with the "element used for reflection/transmission". The element 351 performing channel estimation and the element 351 used for reflection/transmission may each be arranged in the left and right halves of the RIS, or in the top and bottom halves, or in the diagonal halves. In this case, the RIS may generate channel information based on, for example, the channel estimation result of the element 351 performing channel estimation.

(Configuration Example 3)
For example, the element 351 for performing channel estimation and the element 351 for use in reflection/transmission may be arranged at different ratios. For example, the configuration of the RIS of the fourth embodiment may be a configuration in which the "element that does not perform channel estimation of frequency band #1" shown in the above-mentioned FIG. 17 is replaced with the "element that performs channel estimation" and the "element that does not perform channel estimation of frequency band #2" is replaced with the "element that is used for reflection/transmission", respectively. Alternatively, the configuration of the RIS of the fourth embodiment may be a configuration in which the "element that does not perform channel estimation of frequency band #1" shown in the above-mentioned FIG. 17 is replaced with the "element that is used for reflection/transmission" and the "element that does not perform channel estimation of frequency band #2" is replaced with the "element that performs channel estimation", respectively. The RIS may change this ratio according to a predetermined condition. For example, the RIS may change this ratio based on the required accuracy of reflection/transmission and/or the required accuracy of channel estimation. The RIS may acquire information on the conditions for determining the ratio (or information on the ratio itself) from the base station 20 and/or the terminal device 40. This information may be included in the channel estimation form information. In the example of FIG. 17, the RIS may generate channel information based on, for example, a channel estimation result of element 351 that performs channel estimation.

<<5. Modifications>>
The above-described embodiment is merely an example, and various modifications and applications are possible.

For example, the RIS appearing in the above-mentioned embodiments may be a reflecting plate/reflecting sheet capable of controlling the reflection characteristics (e.g., reflection direction/reflectance, etc.), or a transmitting plate/transmitting sheet capable of controlling the transmission characteristics (e.g., refraction direction). The description of the RIS appearing in each of the above-mentioned examples can be replaced with the transmission path control device 30.

In addition, in the above embodiment, the transmission line control device 30 is a device having a structure composed of multiple elements that can change the characteristics related to the reflection and/or transmission of the incoming radio waves. However, the characteristics that the transmission line control device 30 can change are not limited to these. For example, the transmission line control device 30 may be configured to be able to change the radiation angle (directivity) of the reflected and/or transmitted radio waves.

In addition, in the above embodiment, the communication devices that communicate via the transmission path control device 30 (e.g., RIS) were the base station 20 and the terminal device 40, but the communication devices that communicate via the transmission path control device 30 are not limited to these. For example, the communication devices that communicate via the transmission path control device 30 may be the terminal device 40 and another terminal device 40, or the base station 20 and another base station 20. Of course, the communication device may be another communication device such as the management device 10. In this case, the description of the base station 20 and/or the terminal device 40 that appears in the above embodiment can be replaced with a description indicating the other communication device as appropriate.

In addition, in the above-described embodiment, the communication device that transmits the channel estimation signal to the transmission path control device 30 (e.g., RIS) was the base station 20 and/or the terminal device 40, but the communication device that transmits the channel estimation signal is not limited to these. For example, the communication device that transmits the channel estimation signal may be another communication device such as the management device 10. In this case, the description of the base station 20 and/or the terminal device 40 that appears in the above-described embodiment can be replaced with a description indicating the other communication device as appropriate.

In addition, in the above embodiment, the communication device that acquires channel information from the transmission path control device 30 (e.g., RIS) was the base station 20 and/or the terminal device 40, but the communication device that acquires channel information is not limited to these. For example, the communication device that acquires channel information may be another communication device such as the management device 10. In this case, the description of the base station 20 and/or the terminal device 40 that appears in the above embodiment can be replaced with a description indicating the other communication device as appropriate.

In addition, in the above embodiment, only one transmission path control device 30 (e.g., RIS) is installed in the communication environment, but multiple transmission path control devices 30 may be installed. In this case, the multiple transmission path control devices 30 may be centrally controlled by a control station. In this case, the control station may perform the processing performed by the transmission path control device 30 in the above-mentioned channel estimation processing. In other words, the control station may perform processing similar to the processing performed by the control unit 33 provided in the transmission path control device 30. Note that the control station may control only one transmission path control device 30. The control station can be considered as a control device for the transmission path control device 30.

The control device that controls the transmission line control device 30 may be the management device 10, the base station 20, the terminal device 40, the control station, or a control unit thereof (e.g., the control unit 13, the control unit 23, or the control unit 43). The control device that controls the transmission line control device 30 may also be another transmission line control device 30, or the control unit 33 of another transmission line control device 30. Of course, the control device that controls the transmission line control device 30 may also be the control unit 33 of the transmission line control device 30.

The control device that controls the management device 10, base station 20, transmission path control device 30, or terminal device 40 in this embodiment may be realized by a dedicated computer system or a general-purpose computer system.

For example, a program for executing the above-mentioned operations is stored in a computer-readable recording medium such as an optical disk, a semiconductor memory, a magnetic tape, or a flexible disk and distributed. Then, for example, the program is installed in a computer and the above-mentioned processing is executed to configure a control device. In this case, the control device may be a device external to the management device 10, the base station 20, the transmission path control device 30, or the terminal device 40 (for example, a personal computer). Also, the control device may be a device internal to the management device 10, the base station 20, the transmission path control device 30, or the terminal device 40 (for example, the control unit 13, the control unit 23, the control unit 33, or the control unit 43).

The above-mentioned communication program may also be stored on a disk device provided in a server device on a network such as the Internet, so that it can be downloaded to a computer. The above-mentioned functions may also be realized by cooperation between an OS (Operating System) and application software. In this case, the parts other than the OS may be stored on a medium and distributed, or the parts other than the OS may be stored on a server device so that it can be downloaded to a computer.

Furthermore, among the processes described in the above embodiments, all or part of the processes described as being performed automatically can be performed manually, or all or part of the processes described as being performed manually can be performed automatically using known methods. In addition, the information including the processing procedures, specific names, various data and parameters shown in the above documents and drawings can be changed as desired unless otherwise specified. For example, the various information shown in each drawing is not limited to the information shown in the drawings.

Furthermore, each component of each device shown in the figure is a functional concept, and does not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each device is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

The above-described embodiments can be combined as appropriate in areas where the processing content is not inconsistent. The order of each step shown in the sequence diagram or flow chart of this embodiment can be changed as appropriate.

Furthermore, for example, this embodiment can be implemented as any configuration that constitutes an apparatus or system, such as a processor as a system LSI (Large Scale Integration), a module using multiple processors, a unit using multiple modules, a set in which a unit has been further enhanced with other functions, etc. (i.e., a configuration that constitutes part of an apparatus).

In this embodiment, a system refers to a collection of multiple components (devices, modules (parts), etc.), regardless of whether all the components are in the same housing. For example, multiple devices housed in separate housings and connected via a network, etc., and a single device in which multiple modules are housed in a single housing are both systems.

Furthermore, for example, this embodiment can be configured as a cloud computing system in which a single function is shared and processed collaboratively by multiple devices via a network.

<<6. Conclusion>>
As described above, according to this embodiment, the communication system includes a communication device (e.g., a base station 20 and/or a terminal device 40) that communicates in a communication environment in which the transmission path control device 30 is installed, and one or more transmission path control devices 30. The transmission path control device 30 includes a plurality of elements 351 that can change the characteristics related to the reflection or transmission of an incoming radio wave. In the transmission path control device 30, a channel estimation unit 353 is arranged in each of two or more elements 351 out of the plurality of elements 351.

The channel estimation unit performs operations related to channel estimation in the arranged elements 351 based on a channel estimation signal transmitted from the communication device. The control unit 33 of the transmission path control device 30 acquires information related to the results of channel estimation from each channel estimation unit 353. The control unit 33 of the transmission path control device 30 then transmits channel information generated based on the information related to the results of channel estimation to the communication device.

This makes it possible to perform channel estimation for each element 351. As a result, more accurate channel estimation becomes possible, and the transmission path control device 30 and/or the communication device can more precisely control the elements 351 or form the reflected beam. As a result, the communication device can perform high-quality communication via the transmission path control device 30, thereby realizing effective use of radio wave resources.

In addition, the transmission path control device 30 of this embodiment can perform channel estimation for multiple frequency bands and/or propagation paths, thereby reducing overhead caused by channel estimation.

Although each embodiment of the present disclosure has been described above, the technical scope of the present disclosure is not limited to the above-mentioned embodiments as they are, and various modifications are possible without departing from the gist of the present disclosure. Furthermore, components from different embodiments and modified examples may be combined as appropriate.

Furthermore, the effects of each embodiment described in this specification are merely examples and are not limiting, and other effects may also be present.

The present technology can also be configured as follows.
(1)
A transmission path control device having a structure composed of a plurality of elements capable of changing the characteristics related to the reflection or transmission of an incoming radio wave,
An acquisition unit that acquires information regarding a result of channel estimation at each of two or more elements among the plurality of elements;
a transmitter for transmitting channel information based on information on a result of the channel estimation;
A transmission line control device comprising:
(2)
A channel estimator is provided in each of the two or more elements of the plurality of elements, and performs an operation related to channel estimation in the element;
The acquisition unit acquires information based on an operation of the channel estimation unit as information regarding a result of the channel estimation.
The transmission path control device according to (1) above.
(3)
The channel estimation unit is arranged in all elements of the plurality of elements.
The transmission path control device according to (2) above.
(4)
The channel estimation unit is arranged in a part of the plurality of elements.
The transmission path control device according to (2) above.
(5)
The channel estimation unit performs an operation related to the channel estimation based on a signal for the channel estimation transmitted from a communication device.
The transmission line control device according to any one of (2) to (4).
(6)
The transmitting unit transmits the channel information to the communication device.
The transmission path control device according to (5) above.
(7)
A channel estimation control unit that controls an operation of a channel estimation unit arranged in each of the two or more elements,
the channel estimation control unit controls the operation of the channel estimation unit so as to select a channel estimation mode that is predetermined or specified by a communication device among a plurality of channel estimation modes.
The transmission path control device according to any one of (2) to (6).
(8)
A receiving unit that receives information regarding a specified channel estimation mode from a communication device,
The channel estimation control unit controls an operation of the channel estimation unit based on information related to the channel estimation mode.
The transmission path control device according to (7) above.
(9)
The plurality of channel estimation forms include a form in which a channel is estimated for only a single frequency band.
The transmission path control device according to (7) or (8).
(10)
The plurality of channel estimation forms include a form in which different frequency bands are simultaneously estimated.
The transmission path control device according to any one of (7) to (9).
(11)
The plurality of channel estimation modes include a mode in which channel estimation between the transmission path control device and a base station and channel estimation between the transmission path control device and a terminal device are simultaneously performed.
The transmission line control device according to any one of (7) to (10).
(12)
The plurality of channel estimation forms include a form in which the radio wave arriving at the same time as the channel estimation is reflected or transmitted.
The transmission path control device according to any one of (7) to (11).
(13)
The channel information is information obtained by integrating channel estimation results of the two or more elements.
The transmission path control device according to any one of (1) to (12).
(14)
The channel information includes information indicating a channel estimation result of one element among the two or more elements, and information expressed as a difference between the channel estimation result of the one element and another element among the two or more elements,
The transmission path control device according to any one of (1) to (12).
(15)
an interpolation unit that interpolates a channel estimation result for an element for which a channel estimation result has not been obtained among the plurality of elements based on a channel estimation result for an element for which a channel estimation result has been obtained;
The channel information transmitted by the transmitting unit is information based on a plurality of channel estimation results including an interpolated channel estimation result.
The transmission path control device according to any one of (1) to (14).
(16)
a transmission unit that transmits a signal for channel estimation to a transmission path control device that has a structure composed of a plurality of elements that can change the characteristics related to reflection or transmission of an incoming radio wave, and that acquires information on the results of channel estimation at two or more elements among the plurality of elements;
an acquisition unit that acquires channel information based on information on a result of the channel estimation from the transmission path control device;
a communication control unit that controls communication based on the channel information;
A base station comprising:
(17)
a transmission unit that transmits a signal for channel estimation to a transmission path control device that has a structure composed of a plurality of elements that can change the characteristics related to reflection or transmission of an incoming radio wave, and that acquires information on the results of channel estimation at two or more elements among the plurality of elements;
a communication control unit that performs communication using a communication setting determined based on channel information based on information regarding a result of the channel estimation;
A terminal device comprising:
(18)
A method for controlling a transmission path control device having a structure composed of a plurality of elements capable of changing characteristics related to reflection or transmission of an incoming radio wave, comprising the steps of:
obtaining information regarding a result of channel estimation at each of two or more elements of the plurality of elements;
transmitting channel information based on information about the result of the channel estimation;
Control methods.
(19)
a transmission path control device that has a structure composed of a plurality of elements capable of changing a characteristic related to reflection or transmission of an incoming radio wave, and obtains information regarding a result of channel estimation at each of two or more elements among the plurality of elements, and transmits a signal for the channel estimation;
obtaining channel information based on information on the result of the channel estimation from the transmission path control device;
performing communication control based on the channel information;
Communication methods.
(20)
a transmission path control device that has a structure composed of a plurality of elements capable of changing a characteristic related to reflection or transmission of an incoming radio wave, and obtains information regarding a result of channel estimation at each of two or more elements among the plurality of elements, and transmits a signal for the channel estimation;
performing communication using a communication setting determined based on channel information based on information regarding a result of the channel estimation;
Communication methods.

REFERENCE SIGNS LIST 1 Communication system 10 Management device 20 Base station 30 Transmission path control device 40 Terminal device 11, 31 Communication unit 21, 41 Wireless communication unit 12, 22, 32, 42 Storage unit 13, 23, 33, 43 Control unit 24, 34, 44 Sensor unit 35 Surface unit 211, 411 Transmission processing unit 212, 412 Reception processing unit 213, 413 Antenna 231, 331, 431 Acquisition unit 232, 332, 432 Transmission unit 233, 433 Communication control unit 333 Channel estimation control unit 334 Reception unit 335 Interpolation unit 351 Element 352 Phase shifter 353 Channel estimation unit

Claims (20)

A transmission path control device having a structure composed of a plurality of elements capable of changing the characteristics related to the reflection or transmission of an incoming radio wave,
An acquisition unit that acquires information regarding a result of channel estimation at each of two or more elements among the plurality of elements;
a transmitter for transmitting channel information based on information on a result of the channel estimation;
A transmission line control device comprising: A channel estimator is provided in each of the two or more elements of the plurality of elements, and performs an operation related to channel estimation in the element;
The acquisition unit acquires information based on an operation of the channel estimation unit as information regarding a result of the channel estimation.
The transmission line control device according to claim 1 . The channel estimation unit is arranged in all elements of the plurality of elements.
The transmission line control device according to claim 2. The channel estimation unit is arranged in a part of the plurality of elements.
The transmission line control device according to claim 2. The channel estimation unit performs an operation related to the channel estimation based on a signal for the channel estimation transmitted from a communication device.
The transmission line control device according to claim 2. The transmitting unit transmits the channel information to the communication device.
The transmission line control device according to claim 5. A channel estimation control unit that controls an operation of a channel estimation unit arranged in each of the two or more elements,
the channel estimation control unit controls the operation of the channel estimation unit so as to select a channel estimation mode that is predetermined or specified by a communication device among a plurality of channel estimation modes.
The transmission line control device according to claim 2. A receiving unit that receives information regarding a specified channel estimation mode from a communication device,
The channel estimation control unit controls an operation of the channel estimation unit based on information related to the channel estimation mode.
The transmission line control device according to claim 7. The plurality of channel estimation forms include a form in which a channel is estimated for only a single frequency band.
The transmission line control device according to claim 7. The plurality of channel estimation forms include a form in which different frequency bands are simultaneously estimated.
The transmission line control device according to claim 7. The plurality of channel estimation modes include a mode in which channel estimation between the transmission path control device and a base station and channel estimation between the transmission path control device and a terminal device are simultaneously performed.
The transmission line control device according to claim 7. The plurality of channel estimation forms include a form in which a radio wave arriving at the same time as the channel estimation is reflected or transmitted.
The transmission line control device according to claim 7. The channel information is information obtained by integrating channel estimation results of each of the two or more elements.
The transmission line control device according to claim 1 . The channel information includes information indicating a channel estimation result of one element among the two or more elements, and information expressed as a difference between the channel estimation result of the one element and another element among the two or more elements,
The transmission line control device according to claim 1 . an interpolation unit that interpolates a channel estimation result for an element for which a channel estimation result has not been obtained among the plurality of elements based on a channel estimation result for an element for which a channel estimation result has been obtained;
The channel information transmitted by the transmitting unit is information based on a plurality of channel estimation results including an interpolated channel estimation result.
The transmission line control device according to claim 1 . a transmission unit that transmits a signal for channel estimation to a transmission path control device that has a structure composed of a plurality of elements that can change the characteristics related to reflection or transmission of an incoming radio wave, and that acquires information on the results of channel estimation at two or more of the plurality of elements;
an acquisition unit that acquires channel information based on information on a result of the channel estimation from the transmission path control device;
a communication control unit that controls communication based on the channel information;
A base station comprising: a transmission unit that transmits a signal for channel estimation to a transmission path control device that has a structure composed of a plurality of elements that can change the characteristics related to reflection or transmission of an incoming radio wave, and that acquires information on the results of channel estimation at two or more of the plurality of elements;
a communication control unit that performs communication using a communication setting determined based on channel information based on information regarding a result of the channel estimation;
A terminal device comprising: A method for controlling a transmission path control device having a structure composed of a plurality of elements capable of changing characteristics related to reflection or transmission of an incoming radio wave, comprising the steps of:
obtaining information regarding a result of channel estimation at each of two or more elements of the plurality of elements;
transmitting channel information based on information about the result of the channel estimation;
Control methods. a transmission path control device that has a structure composed of a plurality of elements capable of changing a characteristic related to reflection or transmission of an incoming radio wave, and obtains information regarding a result of channel estimation at each of two or more elements among the plurality of elements, and transmits a signal for the channel estimation;
obtaining channel information based on information on the result of the channel estimation from the transmission path control device;
performing communication control based on the channel information;
Communication methods. a transmission path control device that has a structure composed of a plurality of elements capable of changing a characteristic related to reflection or transmission of an incoming radio wave, and obtains information regarding a result of channel estimation at each of two or more elements among the plurality of elements, and transmits a signal for the channel estimation;
performing communication using a communication setting determined based on channel information based on information regarding a result of the channel estimation;
Communication methods.

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