阅读说明：本技术 一种基于反射特性的低能耗自由空间光网络修复方法 (Low-energy-consumption free space optical network restoration method based on reflection characteristics ) 是由 尹荣荣 刘蕾 韩辉 李雅倩 王静 赵凝 于 2020-04-15 设计创作，主要内容包括：本发明提供一种基于反射特性的低能耗自由空间光网络修复方法,其包括以下步骤：在自由空间光网络工作时,根据现有Heartbeat机制监测节点亚死亡状态,获取节点信息；当节点彻底死亡后,通过节点信息确定节点类型,将监测区域划分成规则的网格,根据Neyman-Pearson判决准则,建立Neyman-Pearson模型,确定网格点覆盖状态；通过模型对死亡节点及周围网格点的探测概率进行计算,根据不同节点类型寻找最佳位置修复空洞。本发明提出了改进最小覆盖圆修复方法和能量覆盖综合评价模型,对死亡节点进行分类修复,通过寻找最优修复位置提高网络覆盖,并且引入带镜子的节点,降低能量消耗,延长修复后网络生命期。(The invention provides a low-energy-consumption free space optical network repairing method based on reflection characteristics, which comprises the following steps of: when the free space optical network works, monitoring the sub-death state of the node according to the existing Heartpoint mechanism, and acquiring node information; when the node dies completely, determining the node type through node information, dividing a monitoring area into regular grids, establishing a Neyman-Pearson model according to a Neyman-Pearson judgment criterion, and determining the coverage state of the grid points; and calculating the detection probability of dead nodes and surrounding grid points through the model, and searching the optimal position according to different node types to repair the cavity. The invention provides an improved minimum coverage circle repairing method and an energy coverage comprehensive evaluation model, carries out classified repairing on dead nodes, improves network coverage by searching for an optimal repairing position, and introduces nodes with mirrors, thereby reducing energy consumption and prolonging the network life period after repairing.)

1. A low-energy-consumption free space optical network repairing method based on reflection characteristics is characterized by comprising the following steps:

monitoring the sub-death state of a node according to the existing Heartpoint mechanism and acquiring node information when a free space optical network works;

secondly, after the sub-death nodes die completely, determining the types of the nodes according to the acquired node information, and dividing the nodes into relay type nodes and non-relay type nodes;

step three, determining the coverage state of the grid point where the death node is located and the surrounding grid points,

dividing a monitoring area into regular grids, firstly establishing a Neyman-Pearson model according to a Neyman-Pearson judgment criterion, calculating joint detection probability of a grid point where a death node is located and each peripheral grid point, then setting a threshold value for the detection probability of the grid point, and dividing the coverage state of the grid point into effective coverage, possible coverage and coverage holes according to the comparison relation between the probability and the threshold value;

step four, searching the optimal positions according to the types of dead nodes and the coverage state of peripheral grid points, and respectively repairing the dead nodes;

for non-relay type dead nodes, the repair process is as follows:

s1, respectively selecting coordinate sets of four edge grid points with the maximum and minimum horizontal coordinates and longitudinal coordinates of n void grid points generated by node death according to the coverage states of the grid points where the death nodes are located and the surrounding grid points obtained in the step three, and sequencing the four grid points in a clockwise direction;

s2, connecting the four grid points to form a quadrangle, and making an inscribed circle of the quadrangle;

s3, calculating the center of an inscribed circle, wherein the center of the inscribed circle is the best position for repair;

s4, placing the common node at the optimal position for optical network repair;

for a dead node of a relay type, the repairing process is as follows:

p1, according to the coverage states of the grid points where the death nodes are located and the surrounding grid points obtained in the third step, according to different weight proportions, the sum of the areas of the coverage holes and the possible coverage before repair and the sum of the areas of the coverage holes and the possible coverage after repair are obtained through addition calculation, and the coverage ratio is obtained through comparison of the two areas;

p2, considering an energy model of a mirror node after the mirror is introduced for repair through a free space light energy model;

p3, selecting the node pair whose maximum probability can be reflected by the dead node location;

p4, establishing a comprehensive coverage energy evaluation model through a coverage ratio and an energy model of a mirror node introduced with mirror restoration;

p5, finding the optimal repair position of the node with the mirror through a comprehensive evaluation model under the constraint of establishment of reflection and recovery of the communication area of the communication node through the mirror node;

p6, placing the mirrored repair node in the optimal position, repairing the communication of a pair of node pairs communicating through the node;

p7, other node pair needing to resume communication through the node, selects the communication-capable normal node nearest to the node pair to resume communication.

2. The method according to claim 1, wherein the node information in step one includes node location, node communication mode and location information of a node pair that needs to communicate through the node, and the node pair is composed of a source node and a destination node.

3. A low energy consumption free space optical network repairing method based on reflection characteristic according to claim 1, characterized in that in step two, said relay type node undertakes forwarding task in communication, and said non-relay type node does not undertake forwarding task in communication.

4. The method for repairing a low-energy-consumption free-space optical network based on reflection characteristics as claimed in claim 1, wherein the step P3 is performed by selecting node pairs, wherein the node pairs which need to recover communication through mirror nodes according to dead node information may have a plurality of pairs, different node pairs and dead nodes form different trilaterals, and the node pair closest to the equilateral triangle is selected as the node pair with the maximum probability of being reflected by the dead node position.

5. A low energy consumption free space optical network repairing method based on reflection characteristics as claimed in claim 1 wherein the specific steps of the other nodes needing to recover communication through the node in the step P6 to select the normal communication node nearest to the node to recover communication are as follows:

p61, the communication node needing to be recovered sends a message, which contains the position information of the communication node;

p62, other nodes in communication range receive the message, and send their own position information back to the node according to the position information of the node;

and P63, the node judges the received information, and selects the node with the minimum distance to finish the communication recovery.

6. A low energy consumption free space optical network repairing method based on reflection characteristics as claimed in claim 1 wherein the coverage ratio in P1 step is established as follows:

f＝P₁/P (6)

wherein S is₀To cover the void area before repair, S₁Adding the areas according to different weight proportions to obtain a void value P for possible coverage areas; s₁₀To cover the cavity area after repair, S₁₁Adding the areas according to different weight proportions to obtain a void value P for possible coverage area₁And f is a coverage ratio.

7. A low energy consumption free space optical network restoration method based on reflection characteristics as claimed in claim 1 wherein after introducing mirror restoration in the step P2, the energy model of mirror node is established as follows:

obtaining the energy consumption E of three nodes according to the free space optical communication energy model as follows:

wherein E is_TFor source node energy consumption, E_MFor mirror nodal energy consumption, E_REnergy consumption of destination node, m₁Representing the number of bits of the data packet transmitted by the source node, representing the energy coefficient of the free-space optical wave,is the angle of divergence, l is the communication distance, E_{TX_PE}Representing the energy consumed by the optoelectronic component transmitting the unit bit data, m₂Indicating the number of bits of data packets transmitted by the mirror nodes, E_RXIndicating the need to receive unit bit dataThe energy consumed.

8. The method for repairing a low-energy-consumption free-space optical network based on reflection characteristics according to claim 1, wherein the covering energy comprehensive evaluation model W in the step P2 is:

wherein f is a coverage ratio; and E is node energy consumption.

Technical Field

The invention relates to the technical field of communication, in particular to a low-energy-consumption free space optical network repairing method based on reflection characteristics.

Background

Nowadays, networks have become a very important part of people's lives, and Free Space Optical Networks (FSONs) have the advantages of high transmission data rate, high security, non-standardized spectrum, and the like. In the FSON, once some nodes die due to a failure, coverage holes are caused, more links are also interrupted, and meanwhile, the accuracy of network monitoring data is reduced, so that the network performance is seriously affected, and energy waste is caused. Therefore, how to detect and repair coverage holes and restore the normal operation of the network is a main problem of FSON.

At present, a free space optical network repairing method does not exist, and the traditional wireless network repairing research mainly finds out the optimal repairing position of a coverage hole in a sensor network through a geometric method. And a normal node is newly added according to the position of the repair point, so that the aim of repairing the coverage hole is fulfilled on the premise of ensuring the node redundancy in the network. But the energy consumption of nodes after repair is not considered in the repair method of the newly added normal nodes, so that the network is easily disabled again due to uneven energy consumption.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides an effective repairing method of dead nodes in a free space optical network, on one hand, an improved minimum covering circle repairing method is adopted, the minimum normal nodes are added to replace the dead nodes, the holes caused by the dead nodes are repaired, the network coverage is improved, and the network communication is restored; on the other hand, a comprehensive coverage energy evaluation model is provided, a node with a mirror is creatively introduced for repairing, the condition that the energy consumption of the node is still uneven after repairing until a newly added normal node rapidly dies again is avoided, and the purposes of accurately repairing the cavity and prolonging the life cycle of the network are achieved.

The invention relates to a low-energy-consumption free space optical network repairing method based on reflection characteristics, which comprises the following steps of: monitoring the sub-death state of a node according to the existing Heartpoint mechanism and acquiring node information when a free space optical network works; secondly, after the sub-death nodes die completely, determining the types of the nodes according to the acquired node information, and dividing the nodes into relay type nodes and non-relay type nodes; determining the coverage states of grid points where dead nodes are located and peripheral grid points, dividing a monitoring area into regular grids, firstly establishing a Neyman-Pearson model according to a Neyman-Pearson judgment criterion, calculating the joint detection probability of the grid points where the dead nodes are located and each peripheral grid point, then setting a threshold value for the detection probability of the grid points, and dividing the coverage states of the grid points into effective coverage, possible coverage and coverage holes according to the comparison relationship between the probability and the threshold value; step four, searching the optimal positions according to the types of dead nodes and the coverage state of peripheral grid points, and respectively repairing the dead nodes; for non-relay type dead nodes, the repair process is as follows: s1, respectively selecting coordinate sets of four edge grid points with the maximum and minimum horizontal coordinates and longitudinal coordinates of n void grid points generated by node death according to the coverage states of the grid points where the death nodes are located and the surrounding grid points obtained in the step three, and sequencing the four grid points in a clockwise direction; s2, connecting the four grid points to form a quadrangle, and making an inscribed circle of the quadrangle; s3, calculating the center of an inscribed circle, wherein the center of the inscribed circle is the best position for repair; s4, placing the common node at the optimal position for optical network repair; for a dead node of a relay type, the repairing process is as follows: p1, according to the coverage states of the grid points where the death nodes are located and the surrounding grid points obtained in the third step, according to different weight proportions, the sum of the areas of the coverage holes and the possible coverage before repair and the sum of the areas of the coverage holes and the possible coverage after repair are obtained through addition calculation, and the coverage ratio is obtained through comparison of the two areas; p2, considering an energy model of a mirror node after the mirror is introduced for repair through a free space light energy model; p3, selecting the node pair whose maximum probability can be reflected by the dead node location; p4, establishing a comprehensive coverage energy evaluation model through a coverage ratio and an energy model of a mirror node introduced with mirror restoration; p5, finding the optimal repair position of the node with the mirror through a comprehensive evaluation model under the constraint of establishment of reflection and recovery of the communication area of the communication node through the mirror node; p6, placing the mirrored repair node in the optimal position, repairing the communication of a pair of node pairs communicating through the node; p7, other node pair needing to resume communication through the node, selects the communication-capable normal node nearest to the node pair to resume communication.

Preferably, the node information in the step one includes a node position, a node communication mode and position information of a node pair that needs to communicate through the node, and the node pair is composed of a source node and a destination node.

Preferably, in the second step, the relay-type node undertakes a forwarding task in communication, and the non-relay-type node does not undertake a forwarding task in communication.

Preferably, the process of selecting node pairs in step P3 is that there may be multiple pairs of node pairs that need to resume communication through mirror nodes according to dead node information, different node pairs and dead nodes form different trilaterals, and the node pair closest to the equilateral triangle is selected as the node pair with the maximum probability of being able to reflect through the dead node position.

Preferably, the specific steps of selecting the communication-capable normal node nearest to the other node which needs to recover communication through the node in the step P6 are as follows: p61, the communication node needing to be recovered sends a message, which contains the position information of the communication node; p62, other nodes in communication range receive the message, and send their own position information back to the node according to the position information of the node; and P63, the node judges the received information, and selects the node with the minimum distance to finish the communication recovery.

Preferably, the coverage ratio in step P1 is established as follows:

f＝P₁/P (6)

wherein S is₀To cover the void area before repair, S₁Adding the areas according to different weight proportions to obtain a void value P for possible coverage areas; s₁₀To cover the cavity area after repair, S₁₁Adding the areas according to different weight proportions to obtain a void value P for possible coverage area₁And f is a coverage ratio.

Preferably, after introducing mirror repair in step P2, the energy model of the mirror nodes is established as follows;

obtaining the energy consumption E of three nodes according to the free space optical communication energy model as follows:

wherein E is_TFor source node energy consumption, E_MFor mirror nodal energy consumption, E_REnergy consumption of destination node, m₁Representing the number of bits of the data packet transmitted by the source node, representing the energy coefficient of the free-space optical wave,is the angle of divergence, l is the communication distance, E_{TX_PE}Representing the energy consumed by the optoelectronic component transmitting the unit bit data, m₂Indicating the number of bits of data packets transmitted by the mirror nodes, E_RXIndicating the energy consumed to receive a unit bit of data.

Preferably, the comprehensive evaluation model W of the covering energy in the step P2 is:

wherein f is a coverage ratio; and E is node energy consumption.

The invention has the following effects:

on the premise of providing an improved minimum coverage circle repairing method and a coverage energy comprehensive evaluation model, the method adopts the improved method and the evaluation model to carry out classified repairing on dead nodes, adopts the improved minimum coverage circle repairing method to repair cavities generated by non-relay nodes, and improves network coverage by searching for an optimal repairing position; compared with the common node, the node with the mirror can not only normally transmit and receive messages, but also transmit the messages through mirror reflection. And repairing the cavity generated by the relay node through a coverage energy comprehensive evaluation model, and prolonging the service life of the repaired network.

Drawings

FIG. 1 is a schematic diagram of a non-relay node repair method for a low-energy-consumption free space optical network based on reflection characteristics according to the present invention;

fig. 2 is a schematic diagram of a relay-type node repair of the present invention; and

fig. 3 is a flow chart of the present invention.

In the figure:

1-maximum edge grid point of vertical coordinate; 2-transverse coordinate minimum edge grid point; 3-longitudinal coordinate minimum margin grid point; 4-maximum edge grid point of lateral coordinate; 5-quadrangle; 6-inscribed circle; 7-optimal repair position of non-relay node; 8-polygon; 9-circle center position: 12-perpendicular bisector; 13-a communicable sector area; 14-location area where mirror nodes can be placed; 15-optimal repair position with mirror node.

Detailed Description

The present invention will be described with reference to the accompanying drawings for describing the technical content, achieved objects and effects of the present invention in detail.

As shown in fig. 1-3, the low-energy-consumption free-space optical network repairing method based on reflection characteristics is implemented by the following steps:

firstly, monitoring the sub-death state of a node according to the existing Heartpoint mechanism and acquiring node information when the free space optical network works. The node information includes node position information, a node communication method, and position information of a node pair that needs to communicate through the node. The node pair refers to a source node and a next hop destination node which need to transmit information through the sub-death node.

And secondly, after the sub-dead nodes die completely, judging the types of the dead nodes according to the communication mode in the acquired node information, wherein the nodes bearing the forwarding tasks are relay nodes, and the nodes not bearing the forwarding tasks are non-relay nodes.

Thirdly, dividing the monitoring area into regular grids, establishing a Neyman-Pearson model according to a Neyman-Pearson judgment criterion, and dividing the coverage state of the grid points into three categories (effective coverage, possible coverage and coverage holes), and the following steps:

when a node dies, a monitoring area is divided into N × N unit grids, so that (N +1) × (N +1) unit grid points can be obtained, the grid where the dead node is located and the grids around the dead node are monitored, a Neyman-Pearson model is established according to a Neyman-Pearson judgment criterion, and the probability P that the probability target j of detection of the grid points around the dead node is detected by i is obtained_ijComprises the following steps:

in the formula (I), the compound is shown in the specification,is a cumulative distribution function of a standard normal distribution, α is the false alarm rate, β isSigma is the standard deviation of Gaussian noise; s is the energy of the detection target node, and gamma is a path loss coefficient; r_ijIs the distance between node i and target j.

When there are k nodes in the region, the joint detection probability of the target j being detected is:

calculating the joint detection probability of the death node and each grid point at the periphery according to the formula (2), stopping calculation until the coverage state of the grid points is effective coverage, considering the characteristic of increasing space-time holes in network repair, and setting two threshold values P for the detection probability of each grid point_S1、P_S2The coverage state of the kth mesh point may be defined as:

if the calculated detection probability is less than P_S1Then the grid point is considered as a coverage hole point, and is greater than or equal to P_S1Less than P_S2Then the grid point is considered to be possibly covered, and is greater than or equal to P_S2Then the mesh point is considered to be effectively covered, so that the coverage state of the mesh point is classified into three categories, namely effective coverage, possible coverage and coverage hole.

And fourthly, searching the optimal positions according to the types of the dead nodes and the coverage state of the peripheral grid points, and respectively carrying out classified repair on the dead nodes.

Fifthly, firstly, repairing the non-relay node, and searching the optimal repairing position for repairing by adopting an improved minimum coverage circle repairing method, wherein the steps are as follows:

when the non-relay node dies, according to the coverage states of the grid point where the dead node is located and the surrounding grid points obtained in the third step, obtaining an area formed by the grid points with the coverage states of coverage holes, respectively taking coordinate sets of a longitudinal coordinate maximum edge grid point 1, a transverse coordinate minimum edge grid point 2, a longitudinal coordinate minimum edge grid point 3 and a transverse coordinate maximum edge grid point 4 of n holes generated by each dead node, and sequencing the four edge grid points in a clockwise direction and recording the four edge grid points as U₀＝{(x₁,y₁),(x₂,y₂),(x₃,y₃),(x₄,y₄) Will U₀Four edge points are connected to form a quadrangle 5And making a quadrilateral inscribed circle 6 to obtain the center (x) of the quadrilateral inscribed circle_h,y_h) And the circle center coordinate is the optimal repair position 7 of the non-relay node, and in order to ensure the maximum coverage, the common node is used as a repair node and placed on the circle center coordinate for optical network repair.

And sixthly, repairing the relay node, wherein the steps are as follows:

q1, calculating a coverage ratio according to the coverage state definition;

obtaining the coverage states of the dead nodes and all grid points around the dead nodes according to the formula (3), and calculating the coverage hole area S before repairing₀And possibly covered (possibly empty) areas S₁Adding the areas according to different weight proportions to obtain a void value P; calculating the area of the coverage hole after repair as S₁₀And a possible coverage (possible void) area of S₁₁Adding the areas according to different weight proportions to obtain a void value P₁The formula is established as follows:

f＝P₁/P (6)

wherein S is₀To cover the void area before repair, S₁Adding the areas according to different weight proportions to obtain a void value P for possible coverage areas; s₁₀To cover the cavity area after repair, S₁₁Adding the areas according to different weight proportions to obtain a void value P for possible coverage area₁And f is a coverage ratio.

Q2, through the free space light energy model, consider the energy model of introducing mirror restoration back, mirror node, concrete step is:

after the nodes die, the communication between a source node and a destination node is interrupted through the communication between the dead nodes, a mirror node is added, the communication between the source node and the destination node is recovered through reflection, the source node only needs to send messages to the mirror node, then the mirror node communicates with the destination node through reflection, the mirror node sends messages sensed by the mirror node to the destination node, the destination node needs to receive data sent by the mirror node and the source node, the communication distances from the source node T to the mirror node M and from the mirror node M to the destination node R are the same, and three-node energy consumption E is obtained according to a free space optical communication energy model:

wherein E is_TFor source node energy consumption, E_MFor mirror nodal energy consumption, E_REnergy consumption of destination node, m₁Representing the number of bits of the data packet transmitted by the source node, representing the energy coefficient of the free-space optical wave,is the angle of divergence, l is the communication distance, E_{TX_PE}Representing the energy consumed by the optoelectronic component transmitting the unit bit data, m₂Indicating the number of bits of data packets transmitted by the mirror nodes, E_RXIndicating the energy consumed to receive a unit bit of data.

Q3, obtaining all node pairs needing to communicate through death relay nodes according to the node information obtained through monitoring, forming different trilaterals by different node pairs and death nodes when mirror nodes are added for repair, selecting the node pair with the maximum probability capable of reflecting through the death node position, namely the node pair closest to an equilateral triangle, and taking the node pair as the node pair for recovering communication through the mirror nodes.

Q4, establishing a comprehensive evaluation model of covering energy through a covering ratio and an energy model after introducing mirror restoration, then finding a restoration position with a mirror node through the comprehensive evaluation model under the restriction of establishing reflection and restoring a communication area of the communication node through the mirror node, wherein the specific restoration steps are as follows:

according to the information obtained from the node sub-death state, coordinates of two nodes transmitting information with the death node are respectively T (a, b) and R (c, d), and the position (x, y) of the mirror node M meets the reflection condition, then the coordinate relationship of the mirror node M position and the two nodes communicating is as follows:

y＝-(c-a)/(d-b)x+(d²-b²)+(c²-a²)/2(d-b) (8)

if U ═ c-a)/d-b, N ═ d²-b²)+(c²-a²) And/2 (d-b), according to a polygon 8 formed by cavities around the relay node when the relay node dies, obtaining the position with the best coverage as a circle center position 9 according to a non-relay node mode, wherein the coordinate is (x)_h,y_h) And the distance r from the mirror node is as follows:

from the formula (9), r²And x satisfies a quadratic equation of unity, with the function curve opening upwards at x_coveragebest＝-(UN-x_h-Uy_h)/(1+U²) Is symmetrical, so x is x_coveragebestWhen r is minimum, r gradually increases as x increases or decreases. While the covered hollow area S₁₀And possibly void area S₁₁The distance r between the center of the covering circle and the center of the mirror is increased and decreased accordingly. I.e. the closer x is to x_coveragebestThe smaller r is, the smaller the covered cavity area S₁₀And possibly void area S₁₁The larger, and therefore the larger, the coverage ratio f.

According to the formula (8), the communication distance l between the mirror node and the node pair needing the mirror node to recover communication is known as follows:

as shown in the formula (10), l²X satisfies a quadratic equation of unity, the function curve opens upward, x_energybest＝-(UN-Ub-a)/(1+U₂) Time symmetry, x ═ x_energybestWhen the node cannot reflect through the mirror node, so x cannot get- (UN-Ub-a)/(1+ U)₂) The closer x is to x_energybestThe smaller l. And the energy consumption E of the node increases with the increase of the transmission distance l, namely the closer x is to x_energybestThe smaller the node energy consumption E.

For a dead relay node, according to the formulas (9) and (10), it can be known that the mirror node position simultaneously affects the coverage ratio f and the node energy consumption E, and the extremization standard is carried out on E and f to (0, 1). The larger the coverage is and the smaller the energy is, the better the mirror node position is, so the comprehensive evaluation model W for coverage energy is established as follows:

due to the directionality of free space optical communication, the mirror-equipped repair node not only needs to satisfy the formula (8), that is, on the perpendicular bisector 12 of the line segment formed by the source node T (a, b) and the destination node R (c, d), but also needs to have the source node T in the communicable area with the source node T in the random direction θ and the communicable distance l_maxIf the node M with the mirror meets the requirement that l (T, M) is less than or equal to l_maxAnd with mirror nodesA communicable sector area 13 of the source node T is obtained, a position area 14 where a mirror node can be placed is obtained from the equation (8) and the obtained communicable sector area 13, and in the position area where a mirror node can be placed, a position where W is the maximum, that is, an optimum repair position 15 with a mirror node is found.

Q5, because of the limitation of the communication area of the optical sensor and the number of the sending equipment and the receiving equipment, the node pair which needs to recover communication through the mirror node may have a plurality of pairs, but generally does not exceed three pairs, when the mirror node is added for repair, different node pairs and dead nodes form a trilateral, the node pair which is closest to an equilateral triangle is selected to recover communication through the mirror node, and other nodes which forward messages through the dead relay node look for the normal node which is closest to the dead relay node in the communication area of the dead relay node to be used as the next hop of the dead relay node, so that normal communication is recovered. The method comprises the following steps:

setting other nodes for forwarding messages through dead relay nodes as s, sending messages by the nodes, wherein the messages comprise position information of the nodes, sending the position information of the nodes back to the nodes according to the position information of the nodes when the surrounding nodes are in the communication range of the nodes and receive the messages of the nodes, and adding the position of the nodes in the information packet to the next hop route when the nodes only receive the information packet sent by one node; when a plurality of information packets are received, the distance between the node s and each communicable node is calculated by acquiring the position coordinates of the communicable nodes, the node with the minimum distance is selected, and the node position is added to the next hop route.

The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope defined by the claims of the present invention.