WO2024074013A1

WO2024074013A1 - Terahertz broadband reconfigurable intelligent surface based on vanadium dioxide

Info

Publication number: WO2024074013A1
Application number: PCT/CN2023/082255
Authority: WO
Inventors: Daquan Yang; Tingyang PAN; Weiguang Wang; Yanzhao Hou; Bingchao LIU
Original assignee: Lenovo (Beijing) Ltd.
Priority date: 2023-03-17
Filing date: 2023-03-17
Publication date: 2024-04-11

Abstract

Methods and apparatuses for terahertz broadband reconfigurable intelligent surface based on vanadium dioxide are disclosed. In one embodiment, a RIS device comprises a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to cause the reconfigurable intelligent surface device to: transmit control signaling indicating a set of operating frequencies supported by the reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and receive a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.

Description

TERAHERTZ BROADBAND RECONFIGURABLE INTELLIGENT SURFACE BASED ON VANADIUM DIOXIDE

FIELD

The subject matter disclosed herein generally relates to wireless communications, and more particularly relates to apparatuses for terahertz (THz) broadband reconfigurable intelligent surface (RIS) based on vanadium dioxide (VO₂) .

BACKGROUND

A wireless communications system may include one or multiple network communication devices, such as base stations, which may be otherwise known as an eNodeB (eNB) , a next-generation NodeB (gNB) , or other suitable terminology. Each network communication device, such as a base station may support wireless communications for one or multiple user communication devices, which may be otherwise known as user equipment (UE) , or other suitable terminology. The wireless communications system may support wireless communications with one or multiple user communication devices by utilizing resources of the wireless communication system (e.g., time resources (e.g., symbols, slots, subframes, frames, or the like) or frequency resources (e.g., subcarriers, carriers) . Additionally, the wireless communications system may support wireless communications across various radio access technologies including third generation (3G) radio access technology, fourth generation (4G) radio access technology, fifth generation (5G) radio access technology, among other suitable radio access technologies beyond 5G (e.g., sixth generation (6G) ) .

Some wireless communications systems, for example, that support 6G may utilize THz radio frequency spectrum bands (e.g., 0.735-0.965 THz) to enable high reliability and low latency exchange of information (e.g., control, data, etc. ) , as well as enable effective and efficient establishment and management of connections (also referred to as links) between network communication devices, user communication devices, or any combination thereof. In some implementations, connections utilizing THz radio frequency spectrum bands may experience loss of channel path and line-of-sight problems between the network communication devices, the user communication devices, or any combination thereof, which may adversely impact the reliability and latency exchange of information, as well as the effectiveness of management of the connections between the network communication devices, the user communication devices, or any combination thereof. It may be desirable in some wireless communications systems to deploy RIS to support wireless communications over THz radio frequency spectrum bands and mitigate or decrease the above problems.

BRIEF SUMMARY

Methods and apparatuses for THz broadband RIS device are disclosed.

In one embodiment, a RIS device comprises a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to cause the reconfigurable intelligent surface device to: transmit control signaling indicating a set of operating frequencies supported by the reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and receive a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.

In some embodiment, the reconfigurable intelligent surface device includes a metasurface comprising multiple meta-atoms. Each meta-atom comprises a symmetrical split-ring layer having a structure of symmetrical split-ring, and wherein the symmetrical split-ring is composed of a metal material and at least two symmetrical sheets of VO₂.

The metal material and the at least two symmetrical sheets of VO₂ are configured to form a ring circuit based at least in part on a temperature of the VO₂ satisfying a temperature threshold, for example, the temperature of the VO₂ exceeds a temperature critical point. The ring circuit is configured to break based at least in part on the temperature of the VO₂ not satisfying the temperature threshold, for example, the temperature of the VO₂ is lower than the temperature critical point. The temperature of the VO₂ may be controlled by external excitation.

In some embodiment, an outer radius of the ring circuit is 50 μm and a width of the ring circuit is 30 μm. An opening angle of each sheet of the at least two symmetrical sheets of VO₂ is 20°. An orientation angle of each sheet of the at least two symmetrical sheets of VO₂ is 0°.

In another embodiment, a method performed at a RIS device comprises transmitting control signaling indicating a set of operating frequencies supported by the reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and receiving a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.

In still another embodiment, a base unit comprises a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to cause the base unit to: receive control signaling indicating a set of operating frequencies supported by a reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and transmit a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.

In some embodiment, the processor is further configured to transmit, via the transceiver, a set of power control parameters for UL transmission for at least one of the supported operation frequencies, and wherein, the set of power control parameters for UL transmission for each supported operation frequency is determined according to the reflection efficiency for the supported operation frequency.

In yet another embodiment, a method performed at a base unit comprises receiving control signaling indicating a set of operating frequencies supported by a reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and transmitting a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description of the embodiments briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only some embodiments, and are not therefore to be considered to be limiting of scope, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

Figures 1 (a) and 1 (b) illustrate a RIS device;

Figure 2 (a) and 2 (b) illustrate a three dimensional view and a sectional view of a symmetrical split-ring structure of VO₂ meta-atom;

Figure 2 (c) illustrates an upper view of the symmetrical split-ring structure of VO₂ meta-atom according to this disclosure;

Figure 3 (a) illustrates simulation result of reflection amplitude of the meta-atom;

Figure 3 (b) illustrates simulation result of phase difference between the meta-atoms

Figures 4 (a) -4 (d) show simulation results of the deflected beams;

Figure 5 illustrates a structure of terahertz communication system;

Figure 6 is a schematic flow chart diagram illustrating an embodiment of a method;

Figure 7 is a schematic flow chart diagram illustrating an embodiment of another method; and

Figure 8 is a schematic block diagram illustrating apparatuses according to one embodiment.

The description of elements in each Figure may refer to elements of proceeding figures. Like numbers refer to like elements in all figures, including alternate embodiments of like elements.

DETAILED DESCRIPTION

Figures 1 (a) and 1 (b) illustrates a RIS device (100) .

The RIS device (100) is composed of an array (referred to as metasurface) (110) and an array controller (120) . As shown in Figures 1 (a) and 1 (b) , the metasurface includes a quantity of repeated units distributed on one or more panels, where each unit can be referred to as a meta-atom. When a network communication device, such as a base station (130) is unable to transmit signals (e.g., downlink transmissions) directly to a user communication device, such as a UE1 (e.g., User 140-1) , UE2 (e.g., User 140-2) , . . ., UEn (e.g., User 140-n) , the RIS device (100) operates as a relay that can obtain (e.g., receive) signals from the base station (130) (or another transmission-reception point (TRP) ) and output (e.g., transmit, send, or reflect) the received signals to the user communication devices, such as the UE1 (User 140-1) , UE2 (User 140-2) , . . ., UEn (User 140-n) .

The RIS device may be configured to control a radiation direction of a beam (e.g., a THz beam) . Snell’s formula is used to explain the beam steering function. The RIS device may control a radiation direction of a beam based on Snell’s formula given by Equation (1) :

where θ_i and θ_r define an incident angle and a reflection angle of the THz beam, respectively; λ₀ defines an operating wavelength of the THz beam; n_i defines a refraction index of a medium (e.g., air) above a metasurface which is designed by a VO₂, andcorresponds to a phase gradient endowed by the metasurface.

Various aspects of the present disclosure may determine that the refraction index (n_i) of air (i.e., the medium above the metasurface is air) is equal to 1 under a normal incident THz beam, where the normal incident THz beam means that the incident angle (θ_i) is equal to 0°(i.e., sinθ_i = 0) . The above Equation (1) can be simplified to Equation (2) :

As a result, the reflection angle (which indicates the radiation direction or deflection direction) (θ_r) of the reflected THz beam may be determined according to Equation (3) :

Therefore, the radiation direction of the reflected THz beam by the RIS device (in particular, by the metasurface) can be tuned by changing the phase gradient

In the condition of mirror reflection, the reflection angle is equal to the incident angle. Due to the property of metasurface, when the THz beam is reflected by the metasurface, a steering angle is added to the reflection angle. It means that the reflection direction is deflected or steered by the steering angle caused by the metasurface. That is, the actual reflection angle reflected by the metasurface is equal to the sum of the reflection angle and the steering angel. In this disclosure, the incident angle is equal to 0°. So, the steering angle and the actual reflection angle have the same value. In the following description, the actual reflection angle is referred to as reflection angle. In other words, in the following description, the reflection angle and the steering angle have the same value.

Various aspects of the present disclosure relate to a RIS device supporting THz broadband (e.g., 0.735-0.965 THz) , where a metasurface of the RIS device may be based on vanadium dioxide (VO₂) . For example, each meta-atom shown in Figure 1 (b) may be a VO₂ meta-atom. The VO₂ meta-atoms can be controlled by the controller (120) to control the radiation direction of the reflected THz beam. A field-programmable gate array (FPGA) , which may be used as the controller (120) , may input a sequence to digitally code the metasurface to change the phase gradientof the metasurface in a THz broadband, where the THz broadband includes an operating bandwidth.

Figures 2 (a) and 2 (b) show an example of a symmetrical split-ring structure of each VO₂ meta-atom (200) of the metasurface according to this disclosure. Figure 2 (a) shows a three dimensional view and Figure 2 (b) shows a sectional view. As shown in Figures 2 (a) and 2 (b) , each meta-atom (200) contains three layers: a metal (e.g., gold) reflective layer at the bottom (at the bottom in Figure 2 (a) , and to the right in Figure 2 (b) ) , which can be for example in a thickness of 0.2μm; an insulating layer (which may also be referred to as pattern layer) (e.g., polyimide substrate) in the middle, which can be for example in a thickness of 28μm; and a symmetrical split-ring layer which includes metal (e.g., gold) material and two symmetrical sheets of VO₂ (see Figure 2 (a) ) (at the top in Figure 2 (a) , and to the left in Figure 2 (b) ) , which can be for example in a thickness of 0.2μm. The metal material and the two symmetrical sheets of VO₂ form a symmetrical split-ring resonator (SSRR) . Each meta-atom can occupy an area (e.g., a square with a side of a length of P, which can be for example 140 μm) . The gold material and the two symmetrical sheets of VO₂ form a ring structure as shown in Figure 2 (a) . For example, the outer radius (r) of the ring is 50 μm; and the width (w) of the ring is 30 μm.

An opening angle (α) refers to the angle where each VO₂ sheet occupies within the ring. An orientation angle (β) refers to the angle between x-axis and the angular bisector of the opening angle of each VO₂ sheet.

VO₂ has a unique property, that is, VO₂ has different states at different temperatures. When the temperature is lower than a temperature critical point (e.g., 60°) , VO₂ can be considered as insulation (in insulation state) . When the temperature exceeds the temperature critical point (e.g., 60°) , VO₂ is metallic (in metallic state) . When VO₂ is in the metallic state, a metal ring circuit is formed by the metal (e.g., gold) material and the VO₂ in metallic state. When VO₂ is in the state of insulation, the structure of the ring circuit is broken. Thus, the equivalent circuit when VO₂ is in the metallic state and the equivalent circuit when VO₂ is in the insulation state are completely different. Due to the difference, there is a phase gradient (or phase difference) between the meta-atom (s) in which VO₂ is in the metallic state and the meta-atom (s) in which VO₂ is in the insulation state.

The temperature of VO₂ can be controlled by external excitation (such as bias voltage, excitation current, etc. ) . For example, the controller can apply different bias voltages to different meta-atoms, so that the VO₂ of each meta-atom can be controlled in the metal state (e.g., the temperature of the VO₂ exceeds the temperature critical point) or in the insulation state (e.g., the temperature of the VO₂ is lower than the temperature critical point) .

A phase gradient exists between the meta-atom in which VO₂ is in the metal state and the meta-atom in which VO₂ is in the insulation state.

An upper view of an example meta-atom (200) is shown in Figure 2 (c) . The symmetrical split-ring layer includes gold material and two symmetrical sheets of VO₂. The length of each side of the square for the meta-atom is 140 μm. The outer radius (r) of the ring is 50 μm; and the width (w) of the ring is 30 μm. The opening angle (α) is 20°. The orientation angle (β) is 0°.

The conductivity of the VO₂ in insulating state can be 200 S/m; and the conductivity of the VO₂ in metallic state can be 200,000 S/m.

According to simulation, the reflection amplitude of the meta-atom, where the VO₂ in either insulating state or metallic state, is over 0.7 in THz range as shown in Figure 3 (a) . In addition, the phase difference between the meta-atom in which VO₂ is in insulating state and the meta-atom in which VO₂ is in metallic state reaches 180° ± 20° when the frequency is between 0.735-0.965 THz as shown in Figure 3 (b) .

In THz communication systems, the higher the reflection efficiency of the metasurface, the higher the beam deflection efficiency, and the better the transmission performance of the communication system. Binary bit reflectance ratio (BBRR) can be used to evaluate the reflection efficiency of metasurface. BBRR is defined aswhere Г₀ and Г₁ are the complex reflectance when VO₂ is in insulating state and when VO₂ is in metallic state. It means that BBRR is the ratio of the modulus of the difference between 0₀ and Г₁ to the modulus of their sum. In an ideal condition, Г₀ (when VO₂ is in insulating state) and Г₁ (when VO₂ is in metallic state) have the same amplitude and have a phase difference π. So, in the ideal condition, the sum of Г₀ and Г₁ is zero and BBRR is infinite. In a real condition, the sum of Г₀ and Г₁ corresponds to the components of the unwanted specular reflection. It means that the sum of Г₀ and Г₁ is not zero in the real condition, that is, |Г₀+Г₁| is not zero.

This disclosure proposes that, when VO₂ is used for metasurface, the BBRR should be greater than a threshold, e.g., BBRR>5, to ensure that the metasurface can meet the reflection requirement.

According to the above-described Equation (3) , the simulation of the RIS meta-atom shows that, based on the data shown in Figures 3 (a) and 3 (b) , in the frequency band 0.735-0.965THz, the BBRR is all greater than 5 and reaches a peak of 33.5 at 0.905THz, which means that the proposed metasurface including meta-atoms each of which has a symmetrical split-ring structure meets the condition of beam deflection.

Based on the simulation result in Figure 3 (a) , the reflection efficiencies are different for different frequencies (i.e., for different bands) when VO₂ metasurface is employed. Ideally, it is expected that the reflection efficiency is 100%, i.e., all the energy of the incident beam can be reflected by the metasurface without loss. However, based on the simulation result in Figure 3 (a) , it is impossible to achieve 100%reflection efficiency. Considering that RIS device is used to improve the coverage and to provide a strong path for some UE which is out of the coverage of the gNB, the reflection efficiency is important for the gNB to determine the transmit power of the DL signal and to configure an appropriate set of power control parameters for UL transmission. That is, for the broadband RIS device, a different operation frequency (or frequency band) has a different reflection efficiency. So, for a different operation frequency (or frequency band) , the transmit power of the DL signal shall be determined by the reflection efficiency corresponding to the operation frequency (or frequency band) . In addition, for a different operation frequency (or frequency band) , the gNB shall configure to the UE a set of power control parameters for UL transmission corresponding to the operation frequency (or frequency band) , where the UE transmits UL signal via the RIS device to the gNB.

Accordingly, the RIS device should report, to the gNB, the supported operation frequencies (or frequency bands) , and the reflection efficiency for each of the supported frequencies (or frequency bands) . For example, the RIS device includes a processor and a transceiver, and the processor is configured to transmit, via the transceiver, to the gNB, the supported operation frequencies and the reflection efficiency for each of the supported frequencies.

An example of reporting the supported operation frequencies and the reflection efficiency for each of the supported frequencies is provided as in Table 1.

Table 1

Based on the received supported operation frequencies and the reflection efficiency for each of the supported frequencies, when a gNB transmits DL signal in a supported operation frequency, the transmit power is determined according to the reflection efficiency for the supported operation frequency. In addition, the gNB configures, to the UE, a set of power control parameters for UL transmission (via RIS device) for at least one of the supported operation frequencies, wherein, the set of power control parameters for UL transmission for each supported operation frequency is determined according to the reflection efficiency for the supported operation frequency.

When different phase gradients exist among the meta-atoms of a metasurface, the metasurface demonstrate different reflection angles.

An example of a metasurface is described as follows. The metasurface is composed of 324 meta-atoms, forming an 18×18 array structure. Each meta-atom has the structure as shown in Figure 2 (c) .

Each row of the metasurface can be taken as a unit cell. It means that all meta-atoms (e.g., 18 meta-atoms) in one row are controlled together, i.e., the same external excitation is applied to all meta-atoms within one unit cell. For example, the VO₂ of all meta-atoms in one row can be applied with a same external excitation so that their temperatures are lower than 60°, and accordingly the ring circuit for each meta-atom in the one row is broken. Alternatively, the VO₂ of all meta-atoms in another row (different from the one row) can be applied with another same external excitation so that their temperatures exceed 60°, and accordingly the ring circuit is formed for each meta-atom in the other row.

If ‘0’ represents that the VO₂ of all meta-atoms in one row are applied with an external excitation so that their temperatures are lower than 60°, and ‘1’ represents that the VO₂ of all meta-atoms in one row are applied with an external excitation so that their temperatures exceed 60°; then a sequence of 18 bits can configure the temperature of VO₂ of 18 rows of the metasurface, where each row has 18 meta-atoms.

The sequence of 18 bits can be in a periodical manner. It means that after a number of ‘0’ (s) , the same number of ‘1’ (s) follow; and the periodicity is twice the number of ‘0’ (s) . For example, the sequence of 18 bits can be ‘010101010101010101’ with a periodicity of 2, which can be abbreviated as sequence ‘01’ . For another example, the sequence of 18 bits can be ‘001100110011001100’ with a periodicity of 4, which can be abbreviated as sequence ‘0011’ .

In order to investigate the effect of broadband THz beam deflection, the far-field scattering patterns of metasurface including 18×18 meta-atoms with an input of sequence “0011” (i.e., sequence ‘001100110011001100’ ) from 0.735 THz to 0.965 THz are simulated, where the meta-atoms in each row are encoded identically as either ‘0’ or ‘1’a ccording to the sequence “0011” . That is, if a row is input with ‘0’ , the VO₂ of all meta-atoms in the row are applied with an external excitation so that their temperatures are lower than 60°; and a row is input with ‘1’ , the VO₂ of all meta-atoms in the row are applied with another external excitation so that their temperatures are exceed 60°. Figures 4 (a) -4 (d) show the simulation result. Two deflected beams are observed on ±43.2° at 0.77 THz (figure 4 (a) ) , on ±38° at 0.857 THz (figure 4 (b) ) , on ±36° at 0.902 THz (figure 4 (c) ) and on ±33° at 0.965 THz (figure 4 (d) ) , respectively.

The reflection angles of the beam endowed by the metasurface can be controlled through different sequences. It means that each sequence corresponds to a certain reflection angle for a predetermined frequency, which can be pre-computed and stored in a FPGA. When a certain angle (e.g., 36°) needs to be deflected for a predetermined frequency (e.g., 0.902 THz) , the corresponding sequence is retrieved from the FPGA and applied to the metasurface to achieve the required beam steering angle. The FPGA has an interface with a processor (e.g., digital baseband processor) in the RIS device to receive information of the desired steering angle for the beam, and controls the meta-atoms accordingly. The FPGA can be used to direct the beam to the desired direction for any predetermined frequency within a broadband (e.g., 0.735-0.965 THz) .

Figure 5 illustrates a structure of THz communication system (500) . As shown in Figure 5, the RIS device (in particular, the metasurface) (520) reflects the beam from the base unit (e.g., gNB) (510) to the UE (530) . The RIS device (520) includes a RIS controller (525) which functions as the processor and the FPGA. The THz beam control is realized by controlling the phase gradient of the meta-atoms of the metasurface. For example, a coding sequence (e.g., a coding sequence ID) is sent from the gNB (510) to the RIS controller (525) . Based on the coding sequence ID, the coding sequence is retrieved from the FPGA to apply to the metasurface. For example, each row of the meta-atoms is applied with a ‘0’ or a ‘1’ , so that a predetermined reflection angle (or steering angle) is obtained.

In wireless communication system, the system coverage capability can be evaluated by link budget. Link budget is the calculation of all gains and attenuation in the sending end, communication link, propagation environment (atmosphere, coaxial cable, waveguide, optical fiber, etc. ) and receiving end in a communication system. It is used to estimate the distance that a signal can successfully travel from the transmitting end to the receiving end.

Equation (4) is a simplified formula for calculating link budget: P_R=P_t+G_t+G_R+H-σ²-γ+β_RIS-L, where P_R is the link margin, P_t is transmitting power, G_t is transmitting antenna gain, G_R is receiving antenna gain, H is the low noise amplifier gain (the receiving antenna and the low noise amplifier are in the UE) , σ² is the noise power in transmission, γ is the demodulation receiving threshold, β_RIS is the loss of the RIS metasurface and L is path loss in free space. Free space loss describes the energy loss of electromagnetic waves as they travel through the air.

Equation (5) is the calculation of the path loss L: L=20×log₁₀ (4πDf₀/C) , where D is distance in unit of kilometer, f₀ (GHz) is frequency and C is the speed of light. It can be seen that, for a certain distance, the higher the frequency, the greater the loss.

THz band RIS metasurface has low reflection efficiency. When the reflection amplitude is 70%, energy efficiency is about 20% (which is equivalent to -6.99dB =10log₁₀ (0.2) ) , which is used in link budget for analysis. According to the link loss Equation (5) , at 20%energy efficiency, the maximum transmission distance is about 112m (without considering atmospheric attenuation) if f₀ = 0.85 THz. This distance meets the indoor short distance wireless communication.

Figure 6 is a schematic flow chart diagram illustrating an embodiment of a method 600 according to the present application. In some embodiments, the method 600 is performed by an apparatus, such as a RIS device. In certain embodiments, the method 600 may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

The method 600 may comprise 602 transmitting control signaling indicating a set of operating frequencies supported by the reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and 604 receiving a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.

Figure 7 is a schematic flow chart diagram illustrating an embodiment of a method 700 according to the present application. In some embodiments, the method 700 is performed by an apparatus, such as a base unit. In certain embodiments, the method 700 may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

The method 700 may comprise 702 receiving control signaling indicating a set of operating frequencies supported by a reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and 704 transmitting a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.

In some embodiment, the method further comprises transmitting a set of power control parameters for UL transmission for at least one of the supported operation frequencies, wherein, the set of power control parameters for UL transmission for each supported operation frequency is determined according to the reflection efficiency for the supported operation frequency.

Referring to Figure 8, the RIS device includes a processor, a memory, and a transceiver that is a transmitter and/or a receiver. The processors implement a function, a process, and/or a method which are proposed in Figure 6.

A RIS device comprises a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to cause the reconfigurable intelligent surface device to: transmit control signaling indicating a set of operating frequencies supported by the reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and receive a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.

The gNB (i.e., the base unit) includes a processor, a memory, and a transceiver that is a transmitter and/or a receiver. The processors implement a function, a process, and/or a method which are proposed in Figure 7.

The base unit comprises a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to cause the base unit to: receive control signaling indicating a set of operating frequencies supported by a reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and transmit a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.

This disclosure also proposes a RIS device used for THz transmission, comprising a metasurface composed of multiple meta-atoms, each meta-atom includes a symmetrical split-ring layer has a structure of symmetrical split-ring, the symmetrical split-ring is composed of metal material and two symmetrical sheets of VO₂. In some embodiment, the RIS device includes a metasurface composed of multiple meta-atoms, each meta-atom includes a symmetrical split-ring layer has a structure of symmetrical split-ring, the symmetrical split-ring is composed of metal material and two symmetrical sheets of VO₂. In some embodiment, the metal material and the two symmetrical sheets of VO₂ form a ring circuit when the temperature of the VO₂ exceeds a temperature critical point, and the ring circuit is broken when the temperature of the VO₂ is lower than the temperature critical point. The temperature of the VO₂ may be controlled by external excitation. In some embodiment, the outer radius of the ring is 50 μm; and the width of the ring is 30 μm. In some embodiment, an opening angle of each sheet of VO₂ is 20°, and an orientation angle of each sheet of VO₂ is 0°.

As will be appreciated by one skilled in the art that certain aspects of the embodiments may be embodied as a system, apparatus, method, or program product. Accordingly, embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc. ) or an embodiment combining software and hardware aspects that may generally all be referred to herein as a “circuit” , “module” or “system” . Furthermore, embodiments may take the form of a program product embodied in one or more computer readable storage devices storing machine-readable code, computer readable code, and/or program code, referred to hereafter as “code” . The storage devices may be tangible, non-transitory, and/or non-transmission. The storage devices may not embody signals. In a certain embodiment, the storage devices only employ signals for accessing code.

Certain functional units described in this specification may be labeled as “modules” , in order to more particularly emphasize their independent implementation. For example, a module may be implemented as a hardware circuit comprising custom very-large-scale integration (VLSI) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.

Modules may also be implemented in code and/or software for execution by various types of processors. An identified module of code may, for instance, include one or more physical or logical blocks of executable code which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but, may include disparate instructions stored in different locations which, when joined logically together, include the module and achieve the stated purpose for the module.

Indeed, a module of code may contain a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules and may be embodied in any suitable form and organized within any suitable type of data structure. This operational data may be collected as a single data set or may be distributed over different locations including over different computer readable storage devices. Where a module or portions of a module are implemented in software, the software portions are stored on one or more computer readable storage devices.

Any combination of one or more computer readable medium may be utilized. The computer readable medium may be a computer readable storage medium. The computer readable storage medium may be a storage device storing code. The storage device may be, for example, but need not necessarily be, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

A non-exhaustive list of more specific examples of the storage device would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, random access memory (RAM) , read-only memory (ROM) , erasable programmable read-only memory (EPROM or Flash Memory) , portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

Code for carrying out operations for embodiments may include any number of lines and may be written in any combination of one or more programming languages including an object-oriented programming language such as Python, Ruby, Java, Smalltalk, C++, or the like, and conventional procedural programming languages, such as the "C" programming language, or the like, and/or machine languages such as assembly languages. The code may be executed entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the very last scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN) , or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider) .

Reference throughout this specification to “one embodiment” , “an embodiment” , or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment” , “in an embodiment” , and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but mean “one or more but not all embodiments” unless expressly specified otherwise. The terms “including” , “comprising” , “having” , and variations thereof mean “including but are not limited to” , unless otherwise expressly specified. An enumerated listing of items does not imply that any or all of the items are mutually exclusive, otherwise unless expressly specified. The terms “a” , “an” , and “the” also refer to “one or more” unless otherwise expressly specified.

Furthermore, described features, structures, or characteristics of various embodiments may be combined in any suitable manner. In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid any obscuring of aspects of an embodiment.

Aspects of different embodiments are described below with reference to schematic flowchart diagrams and/or schematic block diagrams of methods, apparatuses, systems, and program products according to embodiments. It will be understood that each block of the schematic flowchart diagrams and/or schematic block diagrams, and combinations of blocks in the schematic flowchart diagrams and/or schematic block diagrams, can be implemented by code. This code may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which are executed via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the schematic flowchart diagrams and/or schematic block diagrams for the block or blocks.

The code may also be stored in a storage device that can direct a computer, other programmable data processing apparatus, or other devices, to function in a particular manner, such that the instructions stored in the storage device produce an article of manufacture including instructions which implement the function specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks.

The code may also be loaded onto a computer, other programmable data processing apparatus, or other devices, to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the code executed on the computer or other programmable apparatus provides processes for implementing the functions specified in the flowchart and/or block diagram block or blocks.

The schematic flowchart diagrams and/or schematic block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of apparatuses, systems, methods and program products according to various embodiments. In this regard, each block in the schematic flowchart diagrams and/or schematic block diagrams may represent a module, segment, or portion of code, which includes one or more executable instructions of the code for implementing the specified logical function (s) .

It should also be noted that in some alternative implementations, the functions noted in the block may occur out of the order noted in the Figures. For example, two blocks shown in succession may substantially be executed concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more blocks, or portions thereof, to the illustrated Figures.

Although various arrow types and line types may be employed in the flowchart and/or block diagrams, they are understood not to limit the scope of the corresponding embodiments. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the depicted embodiment. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted embodiment. It will also be noted that each block of the block diagrams and/or flowchart diagrams, and combinations of blocks in the block diagrams and/or flowchart diagrams, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and code.

Layers of a radio interface protocol may be implemented by the processors. The memories are connected with the processors to store various pieces of information for driving the processors. The transceivers are connected with the processors to transmit and/or receive a radio signal. Needless to say, the transceiver may be implemented as a transmitter to transmit the radio signal and a receiver to receive the radio signal.

The memories may be positioned inside or outside the processors and connected with the processors by various well-known means.

In the embodiments described above, the components and the features of the embodiments are combined in a predetermined form. Each component or feature should be considered as an option unless otherwise expressly stated. Each component or feature may be implemented not to be associated with other components or features. Further, the embodiment may be configured by associating some components and/or features. The order of the operations described in the embodiments may be changed. Some components or features of any embodiment may be included in another embodiment or replaced with the component and the feature corresponding to another embodiment. It is apparent that the claims that are not expressly cited in the claims are combined to form an embodiment or be included in a new claim.

The embodiments may be implemented by hardware, firmware, software, or combinations thereof. In the case of implementation by hardware, according to hardware implementation, the exemplary embodiment described herein may be implemented by using one or more application-specific integrated circuits (ASICs) , digital signal processors (DSPs) , digital signal processing devices (DSPDs) , programmable logic devices (PLDs) , field programmable gate arrays (FPGAs) , processors, controllers, micro-controllers, microprocessors, and the like.

Embodiments may be practiced in other specific forms. The described embodiments are to be considered in all respects to be only illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

A reconfigurable intelligent surface device, comprising:

a transceiver; and

a processor coupled to the transceiver, wherein the processor is configured to cause the reconfigurable intelligent surface device to:

transmit control signaling indicating a set of operating frequencies supported by the reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and

receive a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.
The reconfigurable intelligent surface device of claim 1, wherein the reconfigurable intelligent surface device includes a metasurface comprising multiple meta-atoms.
The reconfigurable intelligent surface device of claim 2, wherein each meta-atom comprises a symmetrical split-ring layer having a structure of symmetrical split-ring, and wherein the symmetrical split-ring is composed of a metal material and at least two symmetrical sheets of VO₂.
The reconfigurable intelligent surface device of claim 3, wherein the metal material and the at least two symmetrical sheets of VO₂ are configured to form a ring circuit based at least in part on a temperature of the VO₂ satisfying a temperature threshold.
The reconfigurable intelligent surface device of claim 4, wherein the ring circuit is configured to break based at least in part on the temperature of the VO₂ not satisfying the temperature threshold.
The reconfigurable intelligent surface device of claim 4, wherein the temperature of the VO₂ is controlled by external excitation.
The reconfigurable intelligent surface device of claim 4, wherein an outer radius of the ring circuit is 50 μm and a width of the ring circuit is 30 μm.
The reconfigurable intelligent surface device of claim 3, wherein an opening angle of each sheet of the at least two symmetrical sheets of VO₂ is 20°.
The reconfigurable intelligent surface device of claim 3, wherein an orientation angle of each sheet of the at least two symmetrical sheets of VO₂ is 0°.
A base unit, comprising:

a transceiver; and

a processor coupled to the transceiver, wherein the processor is configured to cause the base unit to:

receive control signaling indicating a set of operating frequencies supported by a reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and

transmit a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.
The base unit of claim 10, wherein,

the processor is further configured to cause the base unit to transmit a set of power control parameters for UL transmission for at least one of the supported operation frequencies, and

wherein, the set of power control parameters for UL transmission for each supported operation frequency is determined according to the reflection efficiency for the supported operation frequency.
A method performed at a reconfigurable intelligent surface device, comprising:

transmitting control signaling indicating a set of operating frequencies supported by the reconfigurable intelligent surface device and a set of reflection efficiencies associated with the set of operating frequencies; and

receiving a transmission over an operating frequency of the set of operating frequencies supported by the reconfigurable intelligent surface device and using a transmit power based on a reflection efficiency associated with the operating frequency.