阅读说明：本技术 一种基于可重构全息超表面的波束优化方法及系统 (Beam optimization method and system based on reconfigurable holographic super surface ) 是由 张雨童 邓若琪 张浩波 于 2021-09-01 设计创作，主要内容包括：本发明公开了一种基于可重构全息超表面的波束优化方法及系统,该方法包括：将基站和用户的发射方向角和接收方向角划分成不同扇区；基站向用户发射信号；将用户信号接收功率最强的收发扇区对作为第一最佳收发扇区对；用户向基站发射信号；将基站信号接收功率最强的收发扇区对作为第二最佳收发扇区对；根据所述第一最佳收发扇区对和所述第二最佳收发扇区对,确定下行链路的最佳收发扇区对以及上行链路的最佳收发扇区对；将所述下行链路的最佳收发扇区对以及所述上行链路的最佳收发扇区对划分为多个波束,确定最佳收发波束对。采用上述方法能够获得最佳波束赋形方案,从而使系统的用户总数据速率最大化。(The invention discloses a beam optimization method and a system based on a reconfigurable holographic super surface, wherein the method comprises the following steps: dividing the transmitting direction angle and the receiving direction angle of a base station and a user into different sectors; the base station transmits signals to users; taking the transceiving sector pair with the strongest user signal receiving power as a first optimal transceiving sector pair; a user transmits a signal to a base station; taking the transceiving sector pair with the strongest signal receiving power of the base station as a second optimal transceiving sector pair; determining an optimal transceiving sector pair of a downlink and an optimal transceiving sector pair of an uplink according to the first optimal transceiving sector pair and the second optimal transceiving sector pair; and dividing the optimal transceiving sector pair of the downlink and the optimal transceiving sector pair of the uplink into a plurality of beams, and determining an optimal transceiving beam pair. The method can obtain the optimal beamforming scheme, thereby maximizing the total data rate of the users of the system.)

1. A beam optimization method based on a reconfigurable holographic super surface is characterized in that a communication scene applied by the method comprises a base station and a user, wherein the base station is provided with the reconfigurable holographic super surface, and the reconfigurable holographic super surface comprises a feed source, a waveguide and a reconfigurable metamaterial radiation unit array positioned on the waveguide;

the method comprises the following steps:

dividing the transmitting direction angle and the receiving direction angle of a base station and a user into different sectors;

the base station transmits signals to the user, and sequentially traverses all transmitting sectors of the base station and receiving sectors of the user;

taking the transceiving sector pair with the strongest user signal receiving power as a first optimal transceiving sector pair;

the user transmits signals to the base station, and the receiving sectors of all the base stations and the transmitting sectors of the user are traversed in sequence;

taking the transceiving sector pair with the strongest signal receiving power of the base station as a second optimal transceiving sector pair;

determining an optimal transceiving sector pair of a downlink and an optimal transceiving sector pair of an uplink according to the first optimal transceiving sector pair and the second optimal transceiving sector pair;

and dividing the optimal transceiving sector pair of the downlink and the optimal transceiving sector pair of the uplink into a plurality of beams, and determining an optimal transceiving beam pair.

2. The method according to claim 1, wherein determining the optimal transmit-receive sector pair for the downlink and the optimal transmit-receive sector pair for the uplink according to the first optimal transmit-receive sector pair and the second optimal transmit-receive sector pair comprises:

adjusting a receiving sector of a base station to a first optimal receiving sector based on the first optimal transceiving sector pair;

the users transmit feedback signals to the base station and traverse the transmitting sectors of all the users in sequence;

the base station receives a feedback signal sent by a user, and at the moment, the base station and the user both obtain an optimal transceiving sector pair of a downlink;

adjusting the receiving sector of the user to be a second optimal receiving sector based on the second optimal transceiving sector pair;

the base station transmits a feedback signal to the user and sequentially traverses the transmitting sectors of all the base stations;

the user receives the feedback signal from the base station, and at this time, both the base station and the user obtain the optimal transceiving sector pair of the last uplink.

3. A beam optimization system based on a reconfigurable holographic super surface, comprising:

the dividing module is used for dividing the transmitting direction angle and the receiving direction angle of the base station and the user into different sectors;

the first transmitting module is used for transmitting signals to the user by the base station and sequentially traversing all transmitting sectors of the base station and receiving sectors of the user;

a first optimal transceiving sector pair determining module, configured to use the transceiving sector pair with the strongest user receiving power as a first optimal transceiving sector pair;

the second transmitting module is used for transmitting signals to the base station by the user and sequentially traversing all receiving sectors of the base station and transmitting sectors of the user;

a second optimal transceiving sector pair determining module, configured to use the transceiving sector pair with the strongest signal receiving power of the base station as a second optimal transceiving sector pair;

a link optimal transceiving sector pair determining module, configured to determine, according to the first optimal transceiving sector pair and the second optimal transceiving sector pair, an optimal transceiving sector pair for a downlink and an optimal transceiving sector pair for an uplink;

and an optimal transceiving beam pair determining module, configured to divide the optimal transceiving sector pair of the downlink and the optimal transceiving sector pair of the uplink into a plurality of beams, and determine an optimal transceiving beam pair.

4. The beam optimization method based on the reconfigurable holographic super surface of claim 3, wherein the link optimal transceiving sector pair determination module specifically comprises:

a first adjusting unit, configured to adjust a receiving sector of a base station to a first optimal receiving sector based on the first optimal transceiving sector pair;

the first feedback signal transmitting unit is used for transmitting feedback signals to the base station by the users and traversing the transmitting sectors of all the users in sequence;

a first feedback signal receiving unit, configured to receive a feedback signal sent by a user at a base station, where the base station and the user both obtain an optimal transceiving sector pair of a downlink;

a second adjusting unit, configured to adjust the receiving sector of the user to a second optimal receiving sector based on the second optimal transceiving sector pair;

the second feedback signal transmitting unit transmits feedback signals to the user by using the base station and traverses the transmitting sectors of all the base stations in sequence;

and a second feedback signal receiving unit, configured to receive a feedback signal sent by the base station, where the base station and the user both obtain an optimal transceiving sector pair of an uplink.

Technical Field

The invention relates to the technical field of communication, in particular to a beam optimization method and system based on a reconfigurable holographic super surface.

Background

In order to implement ubiquitous intelligent information networks, the upcoming sixth generation (6G) wireless communication puts stringent requirements on antenna technology, such as capacity enhancement and precise beam steering. While the ability of both the widely used dish antennas and phased array antennas to achieve these goals has been met, they all have their own inherent drawbacks that have severely hampered their future development. In particular, dish antennas require heavy and expensive beam steering mechanisms, while phased arrays rely heavily on power amplifiers, consume large amounts of power, have complex phase shifting circuits, and numerous phase shifters, especially in the high frequency band. Therefore, to meet the data requirements of the exponentially growing mobile devices in future 6G wireless systems, more cost-effective and efficient antenna techniques are needed. Among the existing antenna technologies, the holographic antenna is a small-sized, low-power-consumption planar antenna, and is receiving increasing attention due to its multi-beam control capability with low manufacturing cost and low hardware cost. Specifically, the holographic antenna uses a metal patch to construct a holographic pattern on the surface, and records the interference between a reference wave and a target wave according to the interference principle. The radiation characteristics of the reference wave can then be varied by means of the holographic pattern to produce the desired radiation direction.

However, as mobile devices have increased explosively, conventional holographic antennas have presented significant challenges because once the holographic pattern is established, the radiation pattern of the conventional holographic antenna is fixed and thus cannot meet the requirements of mobile communications. Due to the controllability of metamaterials, emerging RHS technologies show great potential in improving the deficiencies of traditional holographic antennas. The RHS is an ultra-light thin plane antenna, and a plurality of metamaterial radiating elements are embedded on the surface of the antenna. In particular, the RHS is excited by the reference wave generated by the antenna feed in the form of a surface wave, making it possible to manufacture an RHS based on Printed Circuit Board (PCB) technology with a compact structure. According to the hologram pattern, each radiation element can generate a desired radiation direction by electrically controlling the radiation amplitude of the reference wave. Therefore, compared with the traditional dish antenna and the traditional phased array antenna, the RHS can realize dynamic beam forming without a heavy mechanical movement device and a complex phase shift circuit, can greatly save the manufacturing cost and the power loss of the antenna, and is very convenient to install due to a light and thin structure.

Since each RHS radiating element corresponds to an antenna element, the channel estimation becomes more complex as the number of elements increases, and the elements of the channel matrix between the RHS and the user also increase. The existing research work in RHS has been mainly focused on RHS hardware component design and radiation direction control, and most of the research only proves the feasibility of the RHS to implement dynamic multi-beam control. At present, no work is carried out on a beam training method of a reconfigurable holographic super surface based on a codebook.

Disclosure of Invention

The invention aims to provide a beam optimization method and a beam optimization system based on a reconfigurable holographic super surface, so that an optimal beam forming scheme is obtained, and the total data rate of users of the system is maximized.

In order to achieve the purpose, the invention provides the following scheme:

a beam optimization method based on a reconfigurable holographic super surface comprises the following steps:

dividing the transmitting direction angle and the receiving direction angle of a base station and a user into different sectors;

the base station transmits signals to the user, and sequentially traverses all transmitting sectors of the base station and receiving sectors of the user;

taking the transceiving sector pair with the strongest user signal receiving power as a first optimal transceiving sector pair;

the user transmits signals to the base station, and the receiving sectors of all the base stations and the transmitting sectors of the user are traversed in sequence;

taking the transceiving sector pair with the strongest signal receiving power of the base station as a second optimal transceiving sector pair;

determining an optimal transceiving sector pair of a downlink and an optimal transceiving sector pair of an uplink according to the first optimal transceiving sector pair and the second optimal transceiving sector pair;

and dividing the optimal transceiving sector pair of the downlink and the optimal transceiving sector pair of the uplink into a plurality of beams, and determining an optimal transceiving beam pair.

Optionally, determining the optimal transceiving sector pair for the downlink and the optimal transceiving sector pair for the uplink according to the first optimal transceiving sector pair and the second optimal transceiving sector pair specifically includes:

adjusting a receiving sector of a base station to a first optimal receiving sector based on the first optimal transceiving sector pair;

the users transmit feedback signals to the base station and traverse the transmitting sectors of all the users in sequence;

the base station receives a feedback signal sent by a user, and at the moment, the base station and the user both obtain an optimal transceiving sector pair of a downlink;

adjusting the receiving sector of the user to be a second optimal receiving sector based on the second optimal transceiving sector pair;

the base station transmits a feedback signal to the user and sequentially traverses the transmitting sectors of all the base stations;

the user receives the feedback signal from the base station, and at this time, both the base station and the user obtain the optimal transceiving sector pair of the last uplink.

The invention also provides a beam optimization system based on the reconfigurable holographic super surface, which comprises the following components:

the dividing module is used for dividing the transmitting direction angle and the receiving direction angle of the base station and the user into different sectors;

the first transmitting module is used for transmitting signals to the user by the base station and sequentially traversing all transmitting sectors of the base station and receiving sectors of the user;

a first optimal transceiving sector pair determining module, configured to use the transceiving sector pair with the strongest user receiving power as a first optimal transceiving sector pair;

the second transmitting module is used for transmitting signals to the base station by the user and sequentially traversing all receiving sectors of the base station and transmitting sectors of the user;

a second optimal transceiving sector pair determining module, configured to use the transceiving sector pair with the strongest signal receiving power of the base station as a second optimal transceiving sector pair;

a link optimal transceiving sector pair determining module, configured to determine, according to the first optimal transceiving sector pair and the second optimal transceiving sector pair, an optimal transceiving sector pair for a downlink and an optimal transceiving sector pair for an uplink;

and an optimal transceiving beam pair determining module, configured to divide the optimal transceiving sector pair of the downlink and the optimal transceiving sector pair of the uplink into a plurality of beams, and determine an optimal transceiving beam pair.

Optionally, the link optimal transceiving sector pair determining module specifically includes:

a first adjusting unit, configured to adjust a receiving sector of a base station to a first optimal receiving sector based on the first optimal transceiving sector pair;

the first feedback signal transmitting unit is used for transmitting feedback signals to the base station by the users and traversing the transmitting sectors of all the users in sequence;

a first feedback signal receiving unit, configured to receive a feedback signal sent by a user at a base station, where the base station and the user both obtain an optimal transceiving sector pair of a downlink;

a second adjusting unit, configured to adjust the receiving sector of the user to a second optimal receiving sector based on the second optimal transceiving sector pair;

the second feedback signal transmitting unit transmits feedback signals to the user by using the base station and traverses the transmitting sectors of all the base stations in sequence;

and a second feedback signal receiving unit, configured to receive a feedback signal sent by the base station, where the base station and the user both obtain an optimal transceiving sector pair of an uplink.

According to the specific embodiment provided by the invention, the invention discloses the following technical effects:

the invention provides a beam optimization method and a system based on a reconfigurable holographic super surface, wherein the method comprises the following steps: dividing the transmitting direction angle and the receiving direction angle of a base station and a user into different sectors; the base station transmits signals to the user, and sequentially traverses all transmitting sectors of the base station and receiving sectors of the user; taking the transceiving sector pair with the strongest user signal receiving power as a first optimal transceiving sector pair; the user transmits signals to the base station, and the receiving sectors of all the base stations and the transmitting sectors of the user are traversed in sequence; taking the transceiving sector pair with the strongest signal receiving power of the base station as a second optimal transceiving sector pair; determining an optimal transceiving sector pair of a downlink and an optimal transceiving sector pair of an uplink according to the first optimal transceiving sector pair and the second optimal transceiving sector pair; and dividing the optimal transceiving sector pair of the downlink and the optimal transceiving sector pair of the uplink into a plurality of beams, and determining an optimal transceiving beam pair. The method can obtain the optimal beamforming scheme, thereby maximizing the total data rate of the users of the system.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a schematic structural view of a reconfigurable holographic metasurface;

FIG. 2 is a schematic diagram of a reconfigurable holographic super-surface signal transmission;

FIG. 3 is a flow chart of wireless communication channel estimation based on a reconfigurable super surface;

FIG. 4 is a flow chart of a beam optimization method based on a reconfigurable holographic super surface.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention aims to provide a beam optimization method and a beam optimization system based on a reconfigurable holographic super surface, so that an optimal beam forming scheme is obtained, and the total data rate of users of the system is maximized.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

As shown in FIG. 1, the reconfigurable holographic super surface is composed of a feed source, a parallel plate waveguide and a metamaterial radiation unit array, wherein the feed source emits electromagnetic waves, and the electromagnetic waves propagate on the parallel plate waveguide in the form of surface waves. As shown in fig. 2, in the transmission process, discrete radiation amplitude adjustment of electromagnetic waves transmitted to the metamaterial radiation unit can be realized by adjusting and controlling the on-off states of a plurality of PIN diodes of each metamaterial radiation unit, wherein the metamaterial radiation unit has a limited number of discrete amplitude adjustable values, the on-off states of the diodes have a one-to-one correspondence relationship with the amplitude values of the electromagnetic waves radiated on the metamaterial radiation unit, and if there are I PIN diodes controlling one metamaterial radiation unit, the unit has 2^IA discrete amplitude adjustable value. Therefore, the bias voltage of the power supply in the meta-surface unit is adjusted to the target bias voltage, and the electromagnetic wave amplitude value radiated on the meta-material radiation unit is the target amplitude value.

Compared with the traditional dish antenna, the antenna is controlled to rotate through a heavy mechanical device to realize the beam control mode, the later maintenance cost is high, the RHS size is small, the PCB technology is used for manufacturing to enable the antenna to be compact and light and thin in structure, the manufacturing cost is greatly reduced, the antenna is easy to directly install on a transmitting device, the good dynamic multi-beam control effect can be achieved by the electric control mode, and therefore the RHS is very suitable for multi-user mobile communication.

RHS low power consumption, the hardware cost is low: although the phased array antenna also controls the beam direction by using electricity, the phased array relies on a large number of phase shifters to control the phase of electromagnetic waves in each antenna, and a large number of power amplifiers are also required, so that the phased array antenna requires a complicated phase shifting circuit, and has large power loss and high hardware cost. Compared with the prior art, the RHS does not need a phase shifter and a complex phase shifting circuit, and can control the difference of the electromagnetic wave energy radiated by each radiating unit by using the switch state of the diode, namely, the beam control can be completed in an amplitude modulation mode, so that the RHS is used for assisting multi-user communication, the power consumption is low, the hardware cost is low, and the RHS has great advantages compared with a phased array antenna.

For the above reconfigurable holographic super surface, the wireless communication Channel estimation method is as shown in fig. 3, and before introducing the wireless communication Channel estimation method, Channel State Information (CSI) is simply introduced.

Channel State Information (CSI): information used to estimate a communication link characteristic includes RI, PTI (Precoding Type Indicator), PMI, CQI. The process of estimating CSI is called channel estimation.

Wherein, ri (rank indication): the user suggests a transmission order to be used by the base station in the downlink transmission.

Pmi (precoding Matrix indicator): the user suggests a precoding matrix to be used by the base station in the downlink transmission. The precoding matrix is selected on the basis of an assumption that the "transmission order indicated by the reported RI" is used.

Cqi (channel Quality indicator): the user uses the CQI to tell the scheduler of the base station the downlink channel quality information the user sees.

As shown in fig. 3, assuming that the channel matrix between the base station and the user is H, when the base station transmits a signal s to the user, the signal received at the user is y ═ Hs + n, where n represents noise. Can be converted into y ═ U ∑ C by singular value decomposition^HTs + n. At this time, it is only necessary to obtain the codebook C without knowing the channel matrix. The codebook can be obtained at both the base station and the user, and when the codebook is applied, a code word which can maximize the channel capacity is selected according to the PMI. In downlink, a base station (transmitting end) and a user (receiving end) select different code words from a codebook to precode and combine signals, the user estimates CSI according to the combined signals, determines the current optimal PMI, and feeds the current optimal PMI back to the transmitting end through a limited feedback link, so that the signal is estimatedA lane matrix.

As shown in fig. 4, specifically, the method for optimizing beams (one beam for each codeword) includes:

step 101: the transmit and receive directive angles for the base station and the users are divided into different sectors.

Step 102: the base station transmits signals to the user, and the transmitting sectors of all the base stations and the receiving sectors of the user are traversed in sequence.

Step 103: and taking the transceiving sector pair with the strongest user signal receiving power as the first optimal transceiving sector pair.

Step 104: the user transmits signals to the base station, and the receiving sectors of all the base stations and the transmitting sectors of the user are traversed in sequence.

Step 105: and taking the transceiving sector pair with the strongest signal receiving power of the base station as a second optimal transceiving sector pair.

Step 106: and determining the optimal transceiving sector pair of the downlink and the optimal transceiving sector pair of the uplink according to the first optimal transceiving sector pair and the second optimal transceiving sector pair.

Step 107: and dividing the optimal transceiving sector pair of the downlink and the optimal transceiving sector pair of the uplink into a plurality of beams, and determining an optimal transceiving beam pair.

Wherein, step 106 specifically includes:

step 1061: adjusting a receiving sector of a base station to a first optimal receiving sector based on the first optimal transceiving sector pair;

step 1062: the users transmit feedback signals to the base station and traverse the transmitting sectors of all the users in sequence;

step 1063: the base station receives a feedback signal sent by a user, and at the moment, the base station and the user both obtain an optimal transceiving sector pair of a downlink;

step 1064: adjusting the receiving sector of the user to be a second optimal receiving sector based on the second optimal transceiving sector pair;

step 1065: the base station transmits a feedback signal to the user and sequentially traverses the transmitting sectors of all the base stations;

step 1066: the user receives the feedback signal from the base station, and at this time, both the base station and the user obtain the optimal transceiving sector pair of the last uplink.

The flow of the two phases of beam optimization is described below, taking as an example the communication between the base station equipped with a reconfigurable holographic super-surface and the user 1.

The first stage is as follows: sector scanning

1. Dividing the transmitting and receiving direction angles of the base station and the user 1 into different sectors roughly;

2. the base station transmits signals to the user 1, and in the step, all transmitting sectors of the base station and receiving sectors of the user 1 are traversed in sequence;

3. user 1 detects the received signal power of different transmitting-receiving sector pairs, and takes the transmitting-receiving sector pair corresponding to the strongest receiving power as the optimal transmitting-receiving sector pair;

4. user 1 transmits signal to base station, in this step, traverse all receiving sectors of base station and transmitting sector of user 1 sequentially;

5. the base station detects the received signal power of different transmitting-receiving sector pairs, and takes the transmitting-receiving sector pair corresponding to the strongest receiving power as the optimal transmitting-receiving sector pair;

6. the base station adjusts the receiving sector of the base station to be in accordance with the best receiving sector on the uplink of the base station of the user 1;

7. user 1 transmits feedback signal to base station, that is, optimal receiving and transmitting sector pair of downlink of user 1 of base station, in this step, traversing transmitting sectors of all users 1 in sequence;

8. the base station receives a feedback signal sent by the user 1, and at the moment, both the base station and the user 1 obtain an optimal transceiving sector pair of a downlink of the user 1 of the base station;

9. user 1 adjusts its own receiving sector to conform to the best receiving sector on the downlink of base station user 1;

10. the base station transmits a feedback signal to the user 1, namely, the optimal receiving and transmitting sector pair of the uplink of the base station of the user 1, and in the step, the transmitting sectors of all the base stations are traversed in sequence;

11. user 1 receives the feedback signal from the base station, and at this time, both the base station and user 1 obtain the optimal transceiving sector pair of the uplink of the base station of user 1.

And a second stage: beam scanning

Each sector is subdivided into finer beams and the best transmit-receive beam pair between the base station and user 1 is found in the same manner as in the first stage.

The method can obtain the optimal beamforming scheme, thereby maximizing the total data rate of the users of the system.

The invention also provides a beam optimization system based on the reconfigurable holographic super surface, which comprises the following components:

the dividing module is used for dividing the transmitting direction angle and the receiving direction angle of the base station and the user into different sectors;

the first transmitting module is used for transmitting signals to the user by the base station and sequentially traversing all transmitting sectors of the base station and receiving sectors of the user;

a first optimal transceiving sector pair determining module, configured to use the transceiving sector pair with the strongest user receiving power as a first optimal transceiving sector pair;

the second transmitting module is used for transmitting signals to the base station by the user and sequentially traversing all receiving sectors of the base station and transmitting sectors of the user;

a second optimal transceiving sector pair determining module, configured to use the transceiving sector pair with the strongest signal receiving power of the base station as a second optimal transceiving sector pair;

a link optimal transceiving sector pair determining module, configured to determine, according to the first optimal transceiving sector pair and the second optimal transceiving sector pair, an optimal transceiving sector pair for a downlink and an optimal transceiving sector pair for an uplink;

and an optimal transceiving beam pair determining module, configured to divide the optimal transceiving sector pair of the downlink and the optimal transceiving sector pair of the uplink into a plurality of beams, and determine an optimal transceiving beam pair.

The link optimal transceiving sector pair determining module specifically includes:

a first adjusting unit, configured to adjust a receiving sector of a base station to a first optimal receiving sector based on the first optimal transceiving sector pair;

the first feedback signal transmitting unit is used for transmitting feedback signals to the base station by the users and traversing the transmitting sectors of all the users in sequence;

a first feedback signal receiving unit, configured to receive a feedback signal sent by a user at a base station, where the base station and the user both obtain an optimal transceiving sector pair of a downlink;

a second adjusting unit, configured to adjust the receiving sector of the user to a second optimal receiving sector based on the second optimal transceiving sector pair;

the second feedback signal transmitting unit transmits feedback signals to the user by using the base station and traverses the transmitting sectors of all the base stations in sequence;

and a second feedback signal receiving unit, configured to receive a feedback signal sent by the base station, where the base station and the user both obtain an optimal transceiving sector pair of an uplink.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.