Cellular coverage optimization method based on reconfigurable refractive metasurface

Abstract

The application discloses a kind of based on reconfigurable refractive metasurface cellular coverage optimization method, it is suitable for the communication system of base station and a cellular user constituted with reconfigurable refractive metasurface antenna, the reconfigurable refractive metasurface antenna is composed of feed and reconfigurable refractive metasurface, including: obtaining communication system parameter;According to the communication system parameter, the center coordinates and angle of reconfigurable refractive metasurface and the center coordinates and angle of feed are designed, to maximize cellular coverage;Based on the center coordinates and angle of reconfigurable refractive metasurface and the center coordinates and angle of feed, reconfigurable refractive metasurface antenna is deployed.The application is applied in cellular base station based on optimized reconfigurable refractive metasurface antenna, reaches and traditional phased array same gain while, obtains the technical solution of lower cost, lower power consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronics, in particular to a cellular coverage optimization method based on reconfigurable refractive metasurface. BACKGROUND

[0002] Massive MIMO is an important part of future wireless communication. In existing massive MIMO systems, traditional phased array antennas are used to realize beamforming. However, traditional phased array has the disadvantages of high power consumption and high cost. In order to solve this problem, recently, people have proposed reconfigurable reflective metasurface antennas. However, this antenna has the following disadvantages: due to the shielding effect of the feed on the reflected wave, the antenna radiation efficiency is not high. Therefore, people have proposed reconfigurable refractive metasurface antennas. Since the reconfigurable refractive metasurface does not have the problem of feed shielding, its radiation efficiency is higher than that of the traditional reconfigurable reflective metasurface antenna. However, existing research on reconfigurable refractive metasurface antennas is basically focused on how to design the antenna to optimize the antenna-related indicators such as bandwidth, loss, etc. There is no work considering the use of reconfigurable refractive metasurface antennas in cellular base stations to increase cellular coverage, and there is also no work considering how to optimize the coverage of the cellular base station in this scenario. SUMMARY

[0003] To overcome the above problems, the present application provides a cellular coverage optimization method based on reconfigurable refractive metasurface, which optimizes the position of the feed relative to the refractive metasurface and the position of the refractive metasurface relative to the ground to obtain the best setting scheme.

[0004] The technical content of the present application includes:

[0005] A cellular coverage optimization method based on reconfigurable refractive metasurface is suitable for a communication system composed of a base station equipped with a reconfigurable refractive metasurface antenna and a cellular user. The reconfigurable refractive metasurface antenna is composed of a feed and a reconfigurable refractive metasurface. The steps include:

[0006] Obtain the communication system parameters, including: transmit power, channel parameters between the feed and the user, user sensitivity and penetration loss margin;

[0007] According to the communication system parameters, design the center coordinates and angles of the reconfigurable refractive metasurface and the center coordinates and angles of the feed to maximize the cellular coverage;

[0008] Based on the center coordinates and angles of the reconfigurable refractive metasurface and the center coordinates and angles of the feed, the reconfigurable refractive metasurface antenna is deployed.

[0009] Further, the feed angle is a vector composed of the elevation angle, the azimuth angle, and the rotation angle of the feed.

[0010] Further, the feed center coordinates Q i and the feed angle T i are defined by a first Cartesian coordinate system, where the first Cartesian coordinate system has the center of the reconfigurable refractive meta-surface as the origin, and the x and y axes are in the directions of the two edges of the reconfigurable refractive meta-surface, and the z axis is in the direction perpendicular to the reconfigurable refractive meta-surface.

[0011] Further, the angle of the reconfigurable refractive meta-surface is a vector composed of the elevation angle, the azimuth angle, and the rotation angle of the angle of the reconfigurable refractive meta-surface.

[0012] Further, the refractive meta-surface center coordinates and the reconfigurable refractive meta-surface angle are defined by a second Cartesian coordinate system, where the second Cartesian coordinate system has the projection of the base station on the ground plane as the origin, the xoy plane is the ground plane, and the z axis is in the direction perpendicular to the ground plane.

[0013] Further, the definition of the cellular coverage includes: γ ≥ γ th = γ s L mar , where γ is the received signal-to-noise ratio of the user, γ th is the received signal-to-noise ratio threshold of the user, γ s is the user sensitivity, and L mar is the penetration loss margin.

[0014] Further, the received signal-to-noise ratio γ of the user is calculated by the following steps:

[0015] 1) According to the center coordinates and the angle of the feed, the antenna gain product G m,n of the transmitting antenna and the receiving antenna in the direction of each unit (m, n) in the reconfigurable refractive meta-surface is calculated.

[0016] 2) According to the refractive meta-surface center coordinates and the refractive meta-surface angle, the distance D m,n from the feed to the unit (m, n) and the distance d m,n from the user to the unit (m, n) are calculated.

[0017] 3) Based on the antenna gain product G m,n , the distance D m,n , and the distance d m,n , the channel gain h m,n of the unit (m, n) is calculated.

[0018] 4) The channel h is calculated by the channel gain h m,n and the refractive coefficient Γ m,n of the unit (m, n).

[0019] 5) Based on the channel h, the feed source transmitting power P and the additive white Gaussian noise variance σ received by the user 2 , the user received signal to noise ratio γ is obtained.

[0020] Further, the center coordinates and angles of the reconfigurable refractive metasurface and the center coordinates and angles of the feed source are obtained by the following steps:

[0021] 1) Keep the feed source center coordinates Q i-1 and the feed source angle T i-1 unchanged, according to the user received signal to noise ratio γ i and the definition of the cell coverage, the optimal cell coverage S i and the corresponding refractive metasurface center coordinates G i and the refractive metasurface angle R i are obtained, wherein i is the iteration number;

[0022] 2) Keep the refractive metasurface center coordinates G i and the refractive metasurface angle R i unchanged, according to the user received signal to noise ratio γ' i and the definition of the cell coverage, the optimal cell coverage S' i and the corresponding feed source center coordinates Q i and the feed source angle T i are obtained;

[0023] 3) When the difference between the optimal cell coverage S' i and the optimal cell coverage S' i+1 is less than a preset threshold, the refractive metasurface center coordinates G i , the refractive metasurface angle R i , the feed source center coordinates Q i , the feed source angle T i are respectively taken as the center coordinates and angles of the reconfigurable refractive metasurface and the center coordinates and angles of the feed source.

[0024] A storage medium, wherein the storage medium stores a computer program, and the computer program is configured to execute the above method when running.

[0025] An electronic device comprising a memory and a processor, wherein the memory stores a program for executing the above method.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] Compared with the prior art, the present application applies the antenna based on the reconfigurable refractive metasurface in the cell base station and optimizes it. While achieving the same gain as the traditional phased array, a technical solution with lower cost and lower power consumption is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Reconfigurable refractive metasurface antenna.

[0029] Figure 2 The method flowchart of the present invention.

[0030] Figure 3 Communication systems based on reconfigurable refractive metasurface antennas.

[0031] Figure 4 A Cartesian coordinate system used to describe the location of the feed source.

[0032] Figure 5 Cartesian coordinates are used to describe the position of a metasurface.

[0033] Figure 6 Flowchart of the cellular coverage optimization method of the present invention.

[0034] Figure 7 A comparison chart of experimental results between the present invention and existing technologies. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only specific embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] A reconfigurable refractive metasurface antenna consists of a feed source and a refractive metasurface. For example... Figure 1 As shown, the refractive metasurface is an array of multiple subwavelength elements. Each element has a PIN diode, which can be switched between ON and OFF by adjusting the bias voltage across it. When a signal is incident on each element, it undergoes refraction. By adjusting the state of the diodes on the elements, the phase of the refracted wave can be changed. The beamforming process of this reconfigurable refractive metasurface antenna is as follows: the signal emitted by the feed is refracted when it is incident on each element. During this refraction process, the metasurface elements apply a certain phase shift to the signal. By adjusting the bias voltage on the diodes, the refraction phase shift of the elements can be appropriately set, thereby achieving beamforming.

[0037] Please refer to Figure 2 and Figure 3 , Figure 2 This is a flowchart of the method of the present invention. Figure 3A communication system based on reconfigurable refractive metasurface antennas. The communication system takes a narrowband downlink network as an example, which contains a user and a base station. We assume that the user is equipped with an omnidirectional antenna. To perform beamforming, the base station employs a reconfigurable refractive metasurface antenna, which effectively serves the users in the 120-degree sector directly in front of the antenna. Assuming that the refractive metasurface contains M*N units, each with a size of s M ×s N . Let the refractive amplitude and phase shift of the (m, n)th unit be A m,n and , respectively. The refractive coefficient of the unit can be written as where the refractive amplitude A m,n can be modeled as represents the incident angle from the feed to the (m, n)th unit. At the same time, we assume that the phase shift of the unit can vary within the range of (0, 2π) when the state of the unit changes, regardless of the incident angle.

[0038] For the convenience of description, we construct a Cartesian coordinate system with the center of the metasurface as the origin and the directions of the two edges of the metasurface as the x and y axes, respectively, and the direction perpendicular to the metasurface as the z axis, as shown in Figure 4 . The position of the feed relative to the metasurface can be described by the coordinates of the center of the feed and the feed's pitch angle, azimuth angle, and rotation angle in this coordinate system, denoted as (x f , y f , z f ) and (θ f , φ f , α f ), respectively. To describe the position of the refractive metasurface relative to the ground, we additionally construct a Cartesian coordinate system. As shown in Figure 5 , the xoy plane of this coordinate system coincides with the ground plane, where the origin o coincides with the projection of the base station on the ground, and the z axis is perpendicular to the ground. For the position of the refractive metasurface relative to the ground, we can describe it by the coordinates of the center of the metasurface and the pitch angle, azimuth angle, and rotation angle of the metasurface in this coordinate system, denoted as (x r , y r , z r ) and (θ r , φ r , α r ), respectively.

[0039] Assume that the channel from the base station feed to the user is composed of M*N super-metasurface-based channels, where the (m, n)th channel represents the channel from the feed via the (m, n)th metasurface unit to the user. The channel gain of the (m, n)th super-metasurface-based channel can be represented as:

[0040]

[0041] where λ represents the wavelength corresponding to the carrier frequency; G m,n represents the product of the antenna gains of the transmitting antenna and the receiving antenna in the direction of the element (m, n), which is affected by the coordinates of the center of the feed and the elevation angle, the azimuth angle, and the rotation angle of the feed; α represents the road loss factor; D m,n and d m,n represent the distance from the feed to the element (m, n) and the distance from the user to the element (m, n), respectively.

[0042] Based on the coordinates of the feed and the metasurface, D m,n and d m,n can be further written as

[0043]

[0044]

[0045] where (x U , y U , z U ) and (x m,n , y m,n , z m,n ) represent the coordinates of the user and the (m, n) element of the metasurface relative to the ground, respectively. Thus, we know that the distance between the feed and the element is affected by the coordinates of the center of the feed, and the distance between the element and the user is affected by the coordinates of the center of the metasurface and the elevation angle, the azimuth angle, and the rotation angle of the metasurface.

[0046] Based on the above, the channel from the feed to the user can be written as

[0047]

[0048] And the received signal-to-noise ratio of the user can be expressed as

[0049]

[0050] where P and σ 2 represent the transmission power of the feed and the variance of the additive white Gaussian noise received by the user, respectively.

[0051] We define the coverage of the base station in a specified sector as the area where the received signal-to-noise ratio of the user is higher than a certain threshold γ th , that is,

[0052] γ≥γ th = γ s L mar ,

[0053] where γ s represents the user sensitivity, L mar represents the excess loss of the transmission. According to the expression of the signal-to-noise ratio, and the definition of the coverage, we can get the relationship between the coverage and the deployment of the feed.

[0054] It is noted that the position of the feed relative to the metasurface, and the position of the metasurface relative to the ground have an impact on the coverage of the base station. In order to optimize the coverage, it is necessary to jointly optimize the position of the feed relative to the refractive metasurface (x f ,y f ,z f ), the pointing of the feed (θ f ,φ f ,α f ), the position of the refractive metasurface relative to the ground (x r ,y r ,z r ), and the pointing of the refractive metasurface (θ r ,φ r ,α r ) as follows:

[0055] As shown in Figure 6 , the present application adopts an iterative algorithm: 1) keeping the position of the feed relative to the metasurface (x f ,y f ,z f ) and (θ f ,φ f ,α f ) unchanged, and optimizing the position of the metasurface relative to the ground (x r ,y r ,z r ) and (θ r ,φ r ,α r ) by mathematical method; 2) keeping the position of the metasurface relative to the ground (x r ,y r ,z r ) and (θ r ,φ r ,α r ) unchanged, and optimizing the position of the feed relative to the metasurface (x f ,y f ,z f ) and (θ f ,φ f ,α f ) by mathematical method; 3) repeating step 1) until the difference of the coverage of two adjacent iterations is less than a preset threshold.

[0056] In an embodiment, the simulation environment is as follows: the base station transmission power is set to 43dBm, the variance of additive white Gaussian noise is set to -96dBm, the operating frequency of the system is set to 26GHz, the user sensitivity is set to 8dB, and the penetration loss margin is set to 30dB. For the reconfigurable refractive metasurface antenna, the directivity pattern of the feed is denoted as G(θ, φ), which is valued as: when G(θ, φ) = 6cos 2 θ; otherwise, G(θ, φ) = 0. The unit transmittance is 0.8, and the size of the unit is where λ is the wavelength corresponding to the operating frequency of the system. For the phased array antenna, the spacing between the array elements is set to half the wavelength, and it is assumed that the array elements are omnidirectional antennas. From the simulation results, as shown in Figure 7 compared with the conventional phased array, the reconfigurable refractive metasurface antenna after the optimized feed and the deployment of the reconfigurable refractive metasurface can provide greater coverage.

[0057] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for optimizing cellular coverage based on reconfigurable refractive metasurfaces, suitable for a communication system consisting of a base station equipped with a reconfigurable refractive metasurface antenna and a cellular user, said reconfigurable refractive metasurface antenna consisting of a feed and a reconfigurable refractive metasurface, The steps include: Obtaining communication system parameters, including: transmit power, channel parameters between feed and user, user sensitivity and penetration loss margin; According to the communication system parameters, the center coordinates and angles of the reconfigurable refractive metasurface and the center coordinates and angles of the feed are designed to maximize the cell coverage; wherein the definition of the cell coverage includes: γ ≥ γ th = γ s L mar , γ is the received signal-to-noise ratio of the user, γ th is the received signal-to-noise ratio threshold of the user, γ s is the user sensitivity, and L mar is the residual penetration loss. Based on the center coordinates and angles of the reconfigurable refractive metasurface and the center coordinates and angles of the feed, the reconfigurable refractive metasurface antenna is deployed. Wherein the center coordinates and angles of the reconfigurable refractive metasurface and the center coordinates and angles of the feed are obtained by the following steps: Keeping the feed center coordinates Q i-1 With the feed angle T i-1 Invariable, according to the user received signal-to-noise ratio γ i With the definition of cellular coverage, the optimal cellular coverage S i And the corresponding refractive metasurface center coordinates G i With the refractive metasurface angle R i Where i is the number of iterations; Keeping the refractive meta-surface center coordinate G i With the refractive meta-surface angle R i Invariable, according to the user received signal-to-noise ratio γ' i With the definition of cellular coverage, the optimal cellular coverage S' is obtained i And the corresponding feed center coordinate Q i With the feed angle T i ; When the optimal cellular coverage S′ i With optimal cellular coverage S′ i+1 When the difference is less than a preset threshold, the center coordinates G of the refractive metasurface will be... i , refractive metasurface angle R i Feed center coordinates Q i Feed angle T i , respectively, serve as the center coordinates and angles of the reconfigurable refractive metasurface, and the center coordinates and angles of the feed source.

2. The method of claim 1, wherein, The feed angle is a vector composed of the pitch angle, azimuth angle and rotation angle of the feed.

3. The method of claim 2, wherein, By the first Cartesian coordinate system, define the feed center coordinates Q i With the feed angle T i Wherein the first Cartesian coordinate system is with the center of the reconfigurable refractive metasurface as the origin, the directions of the two edges of the reconfigurable refractive metasurface are x and y axes respectively, and the direction perpendicular to the reconfigurable refractive metasurface is z axis.

4. The method of claim 1, wherein, The angle of the reconfigurable refractive metasurface is a vector composed of the pitch angle, azimuth angle and rotation angle of the reconfigurable refractive metasurface angle.

5. The method of claim 4, wherein, The center coordinates of the refractive metasurface and the angle of the reconfigurable refractive metasurface are defined by a second Cartesian coordinate system, wherein the second Cartesian coordinate system is with the projection of the base station on the ground as the origin, the ground plane is the xoy plane, and the direction perpendicular to the ground plane is the z axis.

6. The method of claim 1, wherein, The user received signal-to-noise ratio γ is calculated by the following steps: 1) Calculate the product of the antenna gains G in the direction of each unit (m, n) in the reconfigurable refractive meta-surface of the transmitting antenna and the receiving antenna according to the central coordinates and the angle of the feed source m,n ; 2) Calculate the distance D from the feed to the element (m,n) based on the refractive metasurface center coordinates and the refractive metasurface angle m,n and the user to element (m,n) distance d m,n ; 3) based on the antenna gain product G m,n , the distance D m,n , the distance dx ,n , the channel gain h m,n of the unit (m, n) is calculated 4) by the channel gain h m,n with the refractive index of the cell (m, n) Γ m,n , the channel h is calculated; 5) Based on the channel h, the feeder transmit power P and the additive white Gaussian noise variance σ 2 received by the user, the user received signal to noise ratio γ is obtained.

7. A storage medium having stored therein a computer program, wherein, The computer program is arranged to execute the method of any one of claims 1-6 when run. 8.An electronic device comprising a memory and a processor, the memory having stored therein a computer program, the processor being arranged to execute the computer program to perform the method of any one of claims 1-6.

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