WO2023103722A1 - 无人机中继服务位置的确定方法与装置 - Google Patents

无人机中继服务位置的确定方法与装置 Download PDF

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Publication number
WO2023103722A1
WO2023103722A1 PCT/CN2022/131915 CN2022131915W WO2023103722A1 WO 2023103722 A1 WO2023103722 A1 WO 2023103722A1 CN 2022131915 W CN2022131915 W CN 2022131915W WO 2023103722 A1 WO2023103722 A1 WO 2023103722A1
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search
vertical plane
area
point
sight
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PCT/CN2022/131915
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English (en)
French (fr)
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陈俊挺
郑元帅
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香港中文大学（深圳）
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Publication of WO2023103722A1 publication Critical patent/WO2023103722A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/18—Network planning tools
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/18502—Airborne stations
    • H04B7/18504—Aircraft used as relay or high altitude atmospheric platform
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/22—Traffic simulation tools or models
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
    • H04W64/006—Locating users or terminals or network equipment for network management purposes, e.g. mobility management with additional information processing, e.g. for direction or speed determination

Definitions

  • Embodiments of the present invention relate to the technical field of unmanned aerial vehicles, and in particular to a method and device for determining a relay service location of an unmanned aerial vehicle.
  • drones can be used to provide relay The service assists two wireless terminals in information transmission.
  • the relay service location of the UAV directly determines the performance of the relay service. Therefore, the determination of UAV relay service location is very important to improve the performance of relay service.
  • the current method often uses the 3D model of the city to determine the location of the relay service by using the ray tracing method.
  • the method relies on timely, accurate, and fine-grained 3D environmental data, including building locations, structural details, and material data.
  • 3D environmental data including building locations, structural details, and material data.
  • this method is difficult to run on a miniaturized platform such as a UAV due to the huge amount of calculation.
  • Embodiments of the present invention provide a method and device for determining a relay service location of an unmanned aerial vehicle to solve the problem of high search complexity in existing methods.
  • an embodiment of the present invention provides a method for determining a relay service location of a drone, and the drone is used to provide relay services to the first device and the second device, the method comprising:
  • the links between the search start position point and the first device and the second device are all direct-sight links, and the search vertical plane is perpendicular to the ground and separates the first device and the second device the plane or cylinder of the second device;
  • the position search is carried out in the first area and the second area respectively until the altitude is reduced to the minimum flying height of the drone, the first area and the second area are composed of the searched starting position point and The straight line perpendicular to the ground divides the search vertical plane, and the position search includes: if it is in the double direct sight area, search vertically downward in the search vertical plane to increase the value of the objective function; if it is in the non-double direct sight area area, search along the path with a constant distance to the target device in the search vertical plane, and the target device is the first device or the second device;
  • the position point in the search path that is located in the double direct-sight area and obtains the maximum value of the overall objective function is determined as the relay service position of the UAV.
  • the target device if the value of the target function from the current position to the first device is smaller than the value of the target function from the current position to the second device, then the target device is the first device; if the target function from the current position to the first device If the value of the function is greater than or equal to the value of the target function from the current position to the second device, then the target device is the second device.
  • determining the search starting point in the search vertical plane includes:
  • the search vertical plane is a mid-vertical plane passing through the midpoint of the line connecting the first device and the second device; the first area and the second area are composed of The mid-vertical plane is divided by a straight line that searches the starting position point and is perpendicular to the ground.
  • the location search includes:
  • the objective function includes a link capacity function, a link data transmission rate function, a link data transmission accuracy rate function, and a video image quality function.
  • the search vertical plane is a plane or a cylinder separating the first device and the second device, and there is a curve on the plane or cylinder, and on the curve
  • the objective function value of each position point to the first device is equal to the objective function value of the position point to the second device.
  • an embodiment of the present invention provides a device for determining a relay service location of an unmanned aerial vehicle, including:
  • the determination module is used to determine the search start position point in the search vertical plane, the links between the search start position point and the first device and the second device are all direct-sight links, and the search vertical plane is perpendicular to the ground and a plane or cylinder separating the first device and the second device;
  • the search module is used to use the search starting point as the starting point of the search to perform a position search in the first area and the second area until the height is reduced to the minimum flying height of the drone.
  • the first area and the second area are formed by searching
  • the search vertical plane is divided by the starting position point and the straight line perpendicular to the ground.
  • the position search includes: if it is in the double direct-sight area, search vertically downward in the search vertical plane to increase the value of the objective function; if If it is located in the non-double direct-sight area, search along the path with a constant distance to the target device in the search vertical plane, and the target device is the first device or the second device;
  • the selection module is used to determine the position point in the search path that is located in the double direct-sight area and obtains the maximum value of the overall objective function as the relay service position of the UAV.
  • an embodiment of the present invention provides a relay drone, including: a power system, a wireless communication device, at least one processor, and a memory;
  • the power system is used to provide flight power to the UAV
  • the wireless communication device is used to provide a relay service to the first device and the second device;
  • the memory stores computer-executable instructions
  • At least one processor executes the computer-executed instructions stored in the memory, so that the at least one processor executes the method for determining the location of the drone relay service provided in any of the above embodiments.
  • an embodiment of the present invention provides a computer-readable storage medium, where computer-executable instructions are stored in the computer-readable storage medium, and when the computer-executable instructions are executed by a processor, they are used to implement the method provided in any of the above-mentioned embodiments.
  • Method for determining the location of unmanned aerial vehicle relay service is described in detail below.
  • the method and device for determining the UAV relay service location provided by the embodiments of the present invention firstly determine the search starting position point in the search vertical plane, and search the link between the starting position point and the first device and the second device Both are direct-sight links, and the vertical search plane is a plane or cylinder that is perpendicular to the ground and separates the first device and the second device; Carry out the position search until the altitude is reduced to the minimum flying height of the UAV.
  • the first area and the second area are divided by the search vertical plane by a straight line perpendicular to the ground through the searched starting position point.
  • the position search includes: In the direct-view area, search vertically downward in the search vertical plane to increase the value of the objective function; if it is in a non-double direct-view area, search along the path that keeps the distance to the target device constant in the search vertical plane , the target device is the first device or the second device; finally, the position point in the search path that is located in the double direct-sight area and obtains the maximum value of the overall objective function is determined as the relay service position of the UAV.
  • FIG. 1 is a schematic diagram of an application scenario provided by an embodiment of the present invention.
  • Fig. 2 is a schematic diagram of a direct-view link and a non-direct-view link provided by an embodiment of the present invention
  • Fig. 3 is a schematic diagram of a coordinate system provided by an embodiment of the present invention.
  • Fig. 4 is a flow chart of an embodiment of a method for determining a relay service location of an unmanned aerial vehicle provided by the present invention
  • FIG. 5 is a schematic diagram of a linear search vertical plane and an arc search vertical plane provided by an embodiment of the present invention
  • FIG. 6 is a schematic diagram of throughput simulation comparison provided by an embodiment of the present invention.
  • FIG. 7 is a schematic diagram of a search trajectory provided by an embodiment of the present invention.
  • FIG. 8 is a schematic structural diagram of an embodiment of a device for determining a relay service location of a drone provided by the present invention.
  • Fig. 9 is a schematic structural diagram of an embodiment of the relay drone provided by the present invention.
  • connection and “connection” mentioned in this application all include direct and indirect connection (connection) unless otherwise specified.
  • UAVs have flexible mobility and are suitable for use as relays to provide relay services.
  • UAV relay service has broad application prospects, so it has attracted much attention in recent years.
  • UAV can be used to assist communication to provide relay service for two communication devices whose communication is blocked to improve communication quality; in wireless charging scenarios , to perform wireless energy transfer between two devices to increase the effective distance of wireless charging; in the video surveillance scene, the UAV takes real-time pictures of the monitored objects and sends the captured images or videos back to the target device.
  • the location of UAV relay service will inevitably affect the quality of relay service, so it is of great significance to study how to determine the location of UAV relay service.
  • the commonly used methods to determine the UAV relay service location include methods based on statistical models and ray tracing methods.
  • the method based on the statistical model is based on geographical statistical information, such as the statistical distribution of building height and density, etc., and calculates the probability that the link is blocked by obstacles according to the spatial geometric parameters of the air-to-ground channel. Therefore, the optimal location of UAV relay service is deduced.
  • this method can only analyze the quality of the air-to-ground link from a statistical point of view, and cannot judge its blocked state for an exact link, so it cannot guarantee to find the optimal UAV relay service location.
  • the ray tracing method needs to use the 3D model of the city to calculate the quality of the air-to-ground link, which relies on timely, accurate and fine 3D environmental data, including the location of buildings, structural details and material data.
  • 3D model of the city which relies on timely, accurate and fine 3D environmental data, including the location of buildings, structural details and material data.
  • the cost of maintaining an accurate and fine 3D environmental data in time is huge, which is usually unaffordable for wireless communication network operators; even if accurate and fine 3D environmental data is obtained, due to the It is difficult for the method to provide structural features about the spatial distribution of link quality, so when searching for the optimal relay service location of the UAV based on this method, there are usually no rules to follow, the search amount is large, the calculation complexity is high, and the calculation amount is extremely high. Huge and difficult to run on a miniaturized platform like a drone. To sum up, the method for determining the location of the UAV relay service in the prior art still needs to be improved.
  • this application proposes a method and device for determining the relay service location of a drone.
  • search along the path with a constant distance to the target device For example, the search can be performed along the equipotential surface so that the value of the objective function does not decrease.
  • the objective function in this application includes but not limited to link capacity function, link data transmission rate function, link data transmission accuracy rate function, video image quality function and so on.
  • the double line-of-sight area is that the links between the drone and the first device and the second device are all direct-line links (Line-of-sight link).
  • -Sight, LoS direct-line links
  • the non-double line-of-sight area means at least one link between the UAV and the first device and the second device is a non-line-of-sight link (NLoS)
  • the area which includes the area where the links between the UAV and the first device and the second device are all non-line-of-sight links, and there is a direct line of sight between the UAV and the first device and the second device link and the area of a non-line-of-sight link.
  • FIG. 1 is a schematic diagram of an application scenario provided by an embodiment of the present invention.
  • the drone 101 can be used as a relay station to provide the first The device 102 and the second device 103 provide a signal relay service.
  • the first device 102 and the second device 103 can be two mobile terminals, or a mobile terminal and a ground base station; the first device 102 and the second device 103 can also be gathered in two local Multiple mobile terminals in the area. As shown in FIG.
  • the first device 102 may be all or part of the mobile terminals in the elliptical area where the first device 102 is located
  • the second device 103 may be all or part of the mobile terminals in the elliptical area where the second device 103 is located. All or part of the mobile device.
  • the height of the drone is limited to [H min , H max ].
  • H min is the minimum flight height of the UAV
  • H max is the maximum flight height of the UAV. It is understandable that, on the one hand, in order to avoid the UAV from colliding with obstacles in the search area to ensure the flight safety of the UAV, on the other hand, in order to improve the search efficiency, the minimum flight height H min of the UAV is greater than the search area The maximum height of obstacles in the middle. For example, greater than the maximum height of obstacles in the relevant area of the first device 102 and the second device 103 .
  • the link between the UAV and the device may still be blocked by obstacles such as buildings, trees and mountains.
  • the link blocked by obstacles is called Non-Line-of-Sight (NLoS)
  • the link not blocked by obstacles is called Line-of-Sight (Line-of-Sight).
  • Sight, LoS Sight
  • the link between the UAV 101 and the first device 102 is not blocked by obstacles, and is a direct-sight link; the link between the UAV 101 and the second device 103 is blocked by a building Blocking is a non-line-of-sight link. It can be understood that the performance of the LoS link is better than that of the NLoS link under the same conditions.
  • the link capacity, data transmission rate and data transmission accuracy of LoS links are higher than those of NLoS links.
  • Millimeter wave communication, wireless optical communication, etc. are more sensitive to obstacles, and the shading of obstacles will greatly reduce the communication quality, while the monitoring service requires a LoS link, so this embodiment is dedicated to making the UAV to two
  • the links of the device are all LoS links.
  • the area where the link between the UAV and the two devices is a LoS link is called the double direct line of sight area, and the other areas, that is, the links between the UAV and the two devices are all NLoS
  • the link area, and the area where there is one LoS link and one NLoS link between the drone and two devices are called non-dual line-of-sight areas.
  • the link between the drone and the device at a certain location is an unobstructed LoS link
  • the links between the drone and the device at all positions directly above this location are unobstructed LoS links
  • the link between the UAV and the device at a certain location is an obstructed NLoS link
  • the link between the UAV and the device is obstructed at all locations directly below this location NLoS link.
  • the UAV is used to provide relay services to the first device and the second device, if the UAV is in a double line-of-sight area at a certain position, then the UAV is in a double-line-of-sight area at all positions directly above this position. Line-of-sight area; if the drone is in a non-dual line-of-sight area at a certain position, the drone is in a non-dual line-of-sight area at all positions directly below that position.
  • the objective function is a link data transmission rate function, a link data transmission accuracy rate function and other functions
  • the method for determining the location of the UAV relay service provided by the embodiment of the present invention is applicable to the situation where the link capacity is negatively correlated with the distance, that is, when the distance between the UAV and the device increases, the distance between the UAV and the device increases.
  • the link capacity between devices is reduced, for example, for the following link capacity model:
  • x is the three-dimensional space position of the UAV
  • d(x) is the distance from the UAV to the device
  • k, b and a are parameters related to the communication link variables, specifically, the transmission power, channel status, Noise conditions are related to link shielding conditions, and the above parameters are different for different communication links.
  • d(x) is the distance between the drone and the device
  • f(x) is the link capacity. Therefore, in order to improve the performance of the relay service, the UAV should lower its altitude as much as possible and be close to the first device and the second device.
  • the optimal relay service location of UAVs is located on the equipotential surface where the capacity of the communication link between the UAV and the two devices is equal superior.
  • the equipotential surface is formed by the points at which the link capacity values to two user equipments are equal.
  • the link function value between the UAV and the first device is f 1 (d 1 (x))
  • the link function value between the UAV and the second device is f 2 (d 2 (x))
  • d 1 (x) ⁇ xu 1 ⁇
  • the relay service position of the UAV is not equal to the capacity of the communication link between the two devices, then it must be possible to adjust the position so that the link capacity of the better link decreases, and the link capacity of the worse link (bottleneck chain) The link capacity of the road) is increased to achieve a better communication effect than the previous position until the communication link capacity between the UAV and the two devices is equal.
  • the link capacity f(d 1 (x)) between the UAV and the first device is greater than the link capacity f(d 2 (x)) between the UAV and the second device, then in the three-dimensional space , the UAV must be able to find a moving direction to reduce the distance between the UAV and the second device, and correspondingly increase the link capacity f(d 2 (x)) between the UAV and the second device.
  • this direction may increase or decrease the link capacity f(d 1 (x)) between the UAV and the first device, but as long as f(d 1 (x))>f(d 2 (x)) (if the distance is small enough to move in that direction), then moving in that direction must increase the communication link capacity of the system.
  • the best relay service location for UAVs is on the boundary between the dual direct line of sight area and the non-double direct line of sight area.
  • the coordinate system shown in Figure 3 is established.
  • the coordinate system takes the position u 1 of the first device as the coordinate origin O, determines the y-axis along the line connecting the position u 1 of the first device and the position u 2 of the second device, the xOy plane is determined by the horizontal plane, and the x-axis passes through At the location u 1 of the first device, the z-axis is perpendicular to the xOy plane and passes through the location u 1 of the first device.
  • the gray plane in Figure 3 is used to represent any plane parallel to the yOz plane.
  • the dashed line in the gray plane is used to represent the boundary between the double direct vision area and the non-double direct vision area. Above the fold line is the double direct view area, and below the fold line It is a non-double direct vision area. Assuming that the optimal position of the UAV in the gray plane is at point p 2 , as shown in Figure 3, p 2 is not on the boundary between the double direct-view area and the non-double direct-view area, and p 2 reaches the point p 2 of the first device.
  • d(p 2 ,u 1 )
  • d(p 2 ,u 2 )
  • 2 the distance from p 2 to the second device.
  • p 1x p 2x
  • p 1y p 2y
  • 0 ⁇ p 1z ⁇ p 2z so that d(p 1 ,u 1 ) ⁇ d(p 2 ,u 1 ) and d(p 1 ,u 2 ) ⁇ d(p 2 ,u 2 ).
  • the link capacity f(d 1 (p 1 )) of point p 1 is greater than or equal to the link capacity f(d 1 (p 2 )) of point p 2 , which is the same as p 2
  • the optimal location points contradict each other. Therefore, the best relay service location of the UAV is on the boundary between the double direct line of sight area and the non-double direct line of sight area.
  • the present invention also provides a method for determining a relay service location of an unmanned aerial vehicle.
  • FIG. 4 is a flowchart of an embodiment of a method for determining a relay service location of a drone provided by the present invention. As shown in Figure 4, the method provided in this embodiment may include:
  • S101 Determine the search start position point in the search vertical plane.
  • the links between the search start position point and the first device and the second device are all direct-sight links, and the search vertical plane is perpendicular to the ground and separates the first The plane or cylinder of the device and the second device.
  • a plane or cylinder perpendicular to the ground and separating the first device and the second device is selected as the vertical search plane.
  • the best relay service location of the UAV is located in the double direct-sight area, so in this embodiment, the links between the first device and the second device are all direct-sight links. Points as the starting point of the search help to reduce the amount of search and improve search efficiency.
  • the vertical search plane in this embodiment can be a plane or a cylinder. Please refer to FIG. 5 , the left side of FIG. 5 shows a plane, which is a linear search vertical plane, and the right side of FIG. 5 shows a cylinder, which is an arc-shaped search vertical plane.
  • the linear search vertical plane can be determined by the following method: record the position of the first device in Figure 5 as (u 11 , u 12 ,0), and the position of the second device as (u 21 ,u 22 ,0), the maximum flight altitude is recorded as H max , the minimum flight altitude is recorded as H min , define the straight line l 1 passing through the points (u 11 ,u 12 ,H min ) and (u 21 ,u 22 ,H min ) , define the straight line l 2 passing through the points (u 11 , u 12 , H max ) and (u 21 , u 22 , H max ).
  • the intersection point of l 1 and the equipotential surface denote the intersection point of l 2 and the equipotential surface as h 1
  • the straight line on the ground is expressed as l h2
  • the linear search vertical plane can be any plane between l h1 and l h2 that is perpendicular to the ground and separates the first device and the second device.
  • the following manner may be used to determine the search starting position point in the search vertical plane including:
  • the search starting point as the starting point of the search, carry out a position search in the first area and the second area respectively until the height is reduced to the minimum flying height of the drone, and the first area and the second area are determined by the searched starting position Points and straight lines perpendicular to the ground divide the search vertical plane, and the position search includes: if it is in the double direct-sight area, search vertically downward in the search vertical plane to increase the value of the objective function; In the direct view area, the search is performed along a path with a constant distance to the target device in the search vertical plane, and the target device is the first device or the second device.
  • the search vertical plane is divided into the first area and the second area by the straight line perpendicular to the ground through the searched starting position point, and the position search is performed in the two areas respectively, which can improve the search efficiency and avoid Searching in a single direction misses the sweet spot.
  • the links between the UAV and the first device and the second device are both LoS links.
  • the search is performed vertically downward in the search vertical plane, reducing the number of unmanned The distance between the computer and the first device and the second device, since the objective function is negatively correlated with the distance, searching along this direction can increase the value of the objective function.
  • the search is carried out along the path with a constant distance to the target device in the search vertical plane, so that the value of the objective function between the UAV and the target device does not decrease.
  • the target device can be determined in the following manner: if the value of the objective function from the current position to the first device is smaller than the value of the target function from the current position to the second device, the target device is the first equipment; if the value of the target function from the current position to the first device is greater than or equal to the value of the target function from the current position to the second device, then the target device is the second device; if the value of the target function from the current position to the first device The value is equal to the value of the target function from the current position to the second device, then the target device is any one of the first device and the second device. Selecting a device with a small value of the objective function as the target device will help to improve the overall objective function value on the search path.
  • the overall objective function can be understood as the bottleneck objective function value of the link, which is determined by the smaller value of the objective function between the UAV and the first device and the objective function between the UAV and the second device.
  • the value of the objective function at each location on the search path can be stored in advance. It should be noted that, in order to avoid the UAV from colliding with obstacles in the search area, the minimum flying height of the UAV in this embodiment needs to be greater than the maximum height of obstacles in the relevant areas of the first device and the second device to ensure Drone flight safety.
  • the position point in the search path that is located in the double direct-sight area and obtains the maximum overall objective function value is determined as the relay service position of the drone.
  • the value of the overall objective function is determined by the smaller of the value of the objective function between the drone and the first device and the value of the objective function between the drone and the second device.
  • the value of the objective function can be measured through the wireless communication between the UAV and the first device and the second device, and this embodiment does not limit the specific implementation manner.
  • the optimal position of the UAV relay service is affected by the occlusion of the surrounding environment, and the occlusion of the surrounding environment is determined by the terrain, and the terrain usually has no rules to follow, such as buildings, vegetation, etc. may appear in any position, with almost any height. That is, there are no favorable features that can be used in the optimization problem of UAV relay service locations.
  • the optimization problem in three-dimensional space, in the absence of favorable features generally requires a cubic search complexity. Taking the radius of the target area as L as an example, a search path length of O(L 3 ) is required to find the optimal location.
  • the method provided in this embodiment can find an approximately globally optimal UAV relay service location under the condition of linear search complexity.
  • the method provided by this embodiment only needs to search for a length of kL, where k is a constant that has nothing to do with L.
  • the length of the search path is about 400 meters.
  • the search path length is about 100km, and the exhaustive search through three-dimensional space is adopted, and the search path length is about 3000km.
  • the minimum flight altitude is set at about 50m, and the maximum altitude is set at about 200m.
  • the method provided by the embodiment of the present invention has only a linear search complexity, it can still find an approximately globally optimal UAV relay service location.
  • the applicant took the application scenario in which the UAV provides relay communication services for two terminal devices as shown in Figure 1 as an example, and simulated the communication throughput of various methods. After the simulation, please refer to Figure 6 for the simulation results.
  • the performance of the method provided by the embodiment of the present invention is quite close to that of the three-dimensional exhaustive method, and it can bring a huge performance gain compared with the traditional statistical method.
  • the average throughput of various methods is counted, as shown in Table 1, where Hc is the average value of the maximum flight height and the minimum flight height of the UAV.
  • the method for determining the location of the UAV relay service provided by this embodiment first determines the search starting position point in the search vertical plane; Carry out a position search, and the position search includes: if it is located in the double direct-sight area, search vertically downward in the search vertical plane to increase the value of the objective function; if it is located in a non-double direct-sight area, search Search the path with a constant distance to the target device; finally, the position point in the search path that is located in the double direct-sight area and obtains the maximum value of the overall objective function is determined as the relay service position of the UAV.
  • the drone is used to provide relay services to the first device and the second device.
  • the first device and the second device are at the same height and have similar communication conditions (for example, they have similar When transmitting power, antenna gain and other communication parameters)
  • the symmetry condition is satisfied. That is to say, from the perspective of the drone, the first device and the second device are symmetrical.
  • the optimal relay service location is located on the mid-vertical plane with equal distances to the first device and the second device.
  • the mid-vertical plane is a search vertical plane passing through the midpoint of the line connecting the first device and the second device.
  • the search vertical plane is a vertical plane passing through the midpoint of the line connecting the first device and the second device; the first area and the second device The second area is divided into the vertical plane by the straight line that searches the starting position point and is perpendicular to the ground.
  • the position search may include: if it is located in a double direct-sight area, then perform a position search vertically downward in the vertical plane; if it is located in a non-double direct-sight area, then use the first device and the second device
  • the midpoint of is the center of the circle, and the distance from the current position to the center of the circle is the radius, and the position search is performed along the direction away from the search start point.
  • the search vertical plane is a plane or a cylinder separating the first device and the second device, and there is a curve on the plane or cylinder , the objective function value from each position point on the curve to the first device is equal to the objective function value from the position point to the second device.
  • FIG. 7 is a schematic diagram of a search trajectory for searching on the vertical plane when the symmetry condition is satisfied according to an embodiment of the present invention.
  • the plane shown in FIG. 7 is a front view of the mid-vertical plane of the first device and the second device.
  • H max is the maximum flying height of the UAV
  • H min is the minimum flying height of the UAV.
  • Select the coordinates on the mid-vertical plane as ( H max ) is used as the starting point of the search
  • point p (0) as shown in FIG. 7 is the starting point of the search.
  • u 1x is the abscissa of the first device
  • u 1y is the ordinate of the first device
  • u 2x is the abscissa of the second device
  • u 2y is the ordinate of the second device.
  • the search start point is the starting point of the first area and the second area; if the search start point is located in a non-double direct-sight area, the search start point is The position point is used as the starting point of the search, and the first area and the second area are searched step by step along the straight line whose height is the maximum flying height of the drone, and the first searched position in the first area is located in the double direct vision area.
  • the first searched point in the second area located in the double direct vision area is used as the starting point of the second area or a point directly below the search starting point in the first area is used as the second area
  • the starting point of the search, the distance between this point and the target device must be greater than or equal to the distance between the last point searched in the first area and the target device.
  • the search is performed along the arc Does not reduce link capacity.
  • the location point with the largest overall objective function value on the search trajectory of the first area and the second area is determined as the relay service location of the UAV, that is, the location point marked with a five-pointed star in the left area in Figure 7 is the center of the UAV. Following the service location.
  • Fig. 8 is a schematic structural diagram of an embodiment of an apparatus for determining a relay service location of a drone provided by the present invention.
  • the device 80 for determining a relay service location of a drone provided in this embodiment may include: a determination module 801 , a search module 802 and a selection module 803 .
  • the determination module 801 is configured to determine a search start position point in the search vertical plane, the links between the search start position point and the first device and the second device are all direct-sight links, and the search vertical plane is vertical A plane or cylinder that is on the ground and vertically separates the first device and the second device.
  • the search module 802 is used to use the search starting point as the starting point of the search to perform position searches in the first area and the second area until the height is reduced to the minimum flying height of the drone.
  • the first area and the second area are formed by
  • the search vertical plane is divided by the search start point and the straight line perpendicular to the ground.
  • the position search includes: if it is in the double direct-sight area, search vertically downward in the search vertical plane to increase the value of the objective function; If it is located in a non-double direct-sight area, search along a path with a constant distance to the target device in the search vertical plane, and the target device is the first device or the second device.
  • the selection module 803 is used to determine the position point in the search path that is located in the double direct-sight area and obtains the maximum value of the overall objective function as the relay service position of the drone.
  • the device for determining the location of the UAV relay service provided in this embodiment can be used to implement the technical solution of the method embodiment corresponding to FIG. 4 , and its implementation principle and technical effect are similar, and will not be repeated here.
  • the target device is the first device; if the target function from the current position to the first device If the value is greater than or equal to the value of the target function from the current position to the second device, then the target device is the second device.
  • the determination module 801 is used to determine the search starting position point in the search vertical plane may specifically include:
  • the search vertical plane is a mid-vertical plane passing through the midpoint of the line connecting the first device and the second device; the first area and the second area are determined by the searched The vertical plane is divided by the straight line at the starting point and perpendicular to the ground.
  • the search module 802 is also used to perform a position search vertically downward in the mid-vertical plane if it is located in a double direct-sight area;
  • the midpoint of the second device is the center of the circle, and the distance from the current position to the center of the circle is the radius, and the position search is performed along the direction away from the search start point.
  • the objective function includes a link capacity function, a link data transmission rate function, a link data transmission accuracy rate function, and a video image quality function.
  • the minimum flying height of the drone is greater than the maximum height of obstacles in the relevant areas of the first device and the second device.
  • the search vertical plane is a plane or a cylinder separating the first device and the second device.
  • the embodiment of the present invention also provides a relay drone.
  • Fig. 9 is a schematic structural diagram of an embodiment of the relay drone provided by the present invention.
  • the relay drone 90 provided in this embodiment may include: a power system 901 , a wireless communication device 902 , at least one processor 903 and a memory 904 , and the components are connected through a bus 905 .
  • the power system 901 is used to provide flight power to the UAV;
  • the wireless communication device 902 is used to provide relay services to the first device and the second device;
  • the memory 904 stores computer execution instructions; at least one processor 903 executes the instructions stored in the memory.
  • the computer executes the instructions, so that at least one processor 903 executes the method for determining the location of the relay service of the drone as provided in any one of the above embodiments.
  • the memory 904 can be, but not limited to, random access memory (Random Access Memory, referred to as: RAM), read-only memory (Read Only Memory, referred to as: ROM), programmable read-only memory (Programmable Read-Only Memory, referred to as: PROM), Erasable Programmable Read-Only Memory (EPROM for short), Electric Erasable Programmable Read-Only Memory (EEPROM for short), etc.
  • RAM Random Access Memory
  • ROM read-only memory
  • PROM programmable read-only memory
  • PROM Programmable Read-Only Memory
  • EPROM Erasable Programmable Read-Only Memory
  • EEPROM Electric Erasable Programmable Read-Only Memory
  • the software programs and modules in the memory 904 may also include an operating system, which may include various software components and/or drivers for managing system tasks (such as memory management, storage device control, power management, etc.), and It can communicate with various hardware or software components to provide an operating environment for other software components.
  • an operating system which may include various software components and/or drivers for managing system tasks (such as memory management, storage device control, power management, etc.), and It can communicate with various hardware or software components to provide an operating environment for other software components.
  • the processor 903 may be an integrated circuit chip, which has a signal processing capability.
  • the above-mentioned processor 903 may be a general-purpose processor, including a central processing unit (Central Processing Unit, CPU for short), a network processor (Network Processor, NP for short), and the like.
  • Various methods, steps and logic block diagrams disclosed in the embodiments of the present invention may be implemented or executed.
  • a general-purpose processor may be a microprocessor, or the processor may be any conventional processor, or the like. It can be understood that the structure of FIG. 9 is only for illustration, and may include more or less components than those shown in FIG. 9 , or have a configuration different from that shown in FIG. 9 . Each component shown in FIG. 9 may be implemented by hardware and/or software.
  • any tangible, non-transitory computer-readable storage medium may be used, including magnetic storage devices (hard disks, floppy disks, etc.), optical storage devices (CD-ROM, DVD, Blu Ray discs, etc.), flash memory and/or the like .
  • These computer program instructions can be loaded into a general purpose computer, special purpose computer or other programmable data processing apparatus to form a machine, so that these instructions executed on the computer or other programmable data processing apparatus can generate an apparatus for realizing specified functions.
  • These computer program instructions may also be stored in a computer-readable memory which can instruct a computer or other programmable data processing device to operate in a particular manner such that the instructions stored in the computer-readable memory form a Manufactures, including implementing devices for implementing specified functions.
  • Computer program instructions can also be loaded on a computer or other programmable data processing device, thereby performing a series of operational steps on the computer or other programmable device to produce a computer-implemented process, so that the computer or other programmable device Instructions may provide steps for performing specified functions.

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Abstract

本发明提供一种无人机中继服务位置的确定方法与装置，包括：在搜索垂面中确定搜索起始位置点；以搜索起始位置点作为搜索起点，分别在第一区域和第二区域中进行位置搜索，位置搜索包括：若位于双直视区域，则在搜索垂面中垂直向下进行搜索以增大目标函数的取值；若位于非双直视区域，则在搜索垂面中沿着到目标设备距离保持恒定的路径进行搜索；最后将搜索路径中位于双直视区域且取得整体目标函数值最大的位置点确定为无人机的中继服务位置。通过合理设置搜索起始点，并且针对双直视区域和非双直视区域分别制定搜索策略，实现了在线性搜索复杂度情况下，找到近似全局最优的无人机中继服务位置，在追求最优性能的目标上极大地降低了搜索复杂度。

Description

无人机中继服务位置的确定方法与装置 技术领域
本发明实施例涉及无人机技术领域，具体涉及一种无人机中继服务位置的确定方法与装置。
背景技术
随着无线通信技术的演进，多种新兴的通信技术对信道的直视条件有较高要求。比如毫米波、太赫兹、自由光、可见光通信等都要求建立直视或近似直视的通信链路。然而，在城市场景下，由于通信设备的移动性，直视条件难以获得保证。另一方面，无人机能够在三维空间中自由移动，可以协助建立直视信道，并用于提供中继服务和视频监控服务。随着无人机技术的不断发展，无人机已经在无线通信、光通信、无线充电、视频监控、动态跟踪和无线能量传输等诸多场景下提供中继服务。以无线通信场景为例，当两个无线终端的之间的无线通信链路由于受到周围建筑物、树木等障碍物的遮挡，而无法达到通信服务质量要求时，可以采用无人机提供中继服务，协助两个无线终端进行信息传递。无人机的中继服务位置直接决定了中继服务的性能。因此无人机中继服务位置的确定对于提升中继服务性能来说至关重要。
现方法常借助于城市的三维模型，利用射线追踪方法来确定中继服务位置。该方法依赖于及时、准确和精细的三维环境数据，包括建筑物的位置、结构细节和材料数据等。然而在实际情况下，城市的发展与变迁日新月异，要及时地维护一个准确和精细的三维环境数据成本巨大。而且即使拥有了准确和精细的三维环境数据，该方法由于计算量极其巨大也难以在无人机这样的小型化平台上运行。
发明内容
本发明实施例提供一种无人机中继服务位置的确定方法与装置，用以解决现有方法搜索复杂度大的问题。
第一方面，本发明实施例提供一种无人机中继服务位置的确定方法，无人机用于向第一设备和第二设备提供中继服务，所述方法包括：
在搜索垂面中确定搜索起始位置点，搜索起始位置点与第一设备和第二设备之间的链路均为直视链路，搜索垂面为垂直于地面且分隔第一设备和第二设备的平面或者柱面；
以搜索起始位置点作为搜索起点，分别在第一区域和第二区域中进行位置搜索直至高度降低至无人机的最小飞行高度，第一区域和第二区域由经搜索起始位置点且与地面垂直的直线将搜索垂面划分而成，位置搜索包括：若位于双直视区域，则 在搜索垂面中垂直向下进行搜索以增大目标函数的取值；若位于非双直视区域，则在搜索垂面中沿着到目标设备距离保持恒定的路径进行搜索，目标设备为第一设备或者第二设备；
将搜索路径中位于双直视区域且取得整体目标函数值最大的位置点确定为无人机的中继服务位置。
一种实施例中，若当前位置到第一设备的目标函数的取值小于当前位置到第二设备的目标函数的取值，则目标设备为第一设备；若当前位置到第一设备的目标函数的取值大于等于当前位置到第二设备的目标函数的取值，则目标设备为第二设备。
一种实施例中，在搜索垂面中确定搜索起始位置点包括：
在搜索垂面中从无人机的最小飞行高度向上搜索，若达到无人机的最大飞行高度，则在搜索垂面中向两侧搜索，直至在搜索垂面中找到与第一设备和第二设备之间的链路均为直视链路的位置点，确定为搜索起始位置点；
或者，
从第一设备正上方最大飞行高度处向第二设备正上方最大飞行高度处，或者，从第二设备正上方最大飞行高度处向第一设备正上方最大飞行高度处搜索，直至到达搜索垂面，若此时无人机与第一设备和第二设备之间的链路均为直视链路，则将该位置点确定为搜索起始位置点；反之，则在搜索垂面中向两侧搜索，直至在搜索垂面中找到与第一设备和第二设备之间的链路均为直视链路的位置点，确定为搜索起始位置点。
一种实施例中，当第一设备和第二设备满足对称性条件时，搜索垂面为经过第一设备和第二设备连线的中点的中垂面；第一区域和第二区域由经搜索起始位置点且与地面垂直的直线将中垂面划分而成。
一种实施例中，位置搜索包括：
若位于双直视区域，则在中垂面中垂直向下进行位置搜索；
若位于非双直视区域，则在中垂面中以第一设备和第二设备的中点为圆心，以当前位置至圆心的距离为半径的圆弧上，沿着远离搜索起始位置点的方向进行位置搜索。
一种实施例中，目标函数包括链路容量函数、链路数据传输速率函数、链路数据传输准确率函数和视频图像质量函数。
一种实施例中，当第一设备和第二设备不满足对称性条件时，搜索垂面为分隔第一设备和第二设备的平面或柱面，平面或柱面上存在一条曲线，曲线上每一位置点到第一设备的目标函数值等于该位置点到第二设备的目标函数值。
第二方面，本发明实施例提供一种无人机中继服务位置的确定装置，包括：
确定模块，用于在搜索垂面中确定搜索起始位置点，搜索起始位置点与第一设 备和第二设备之间的链路均为直视链路，搜索垂面为垂直于地面且分隔第一设备和第二设备的平面或者柱面；
搜索模块，用于以搜索起始位置点作为搜索起点，分别在第一区域和第二区域中进行位置搜索直至高度降低至无人机的最小飞行高度，第一区域和第二区域由经搜索起始位置点且与地面垂直的直线将搜索垂面划分而成，位置搜索包括：若位于双直视区域，则在搜索垂面中垂直向下进行搜索以增大目标函数的取值；若位于非双直视区域，则在搜索垂面中沿着到目标设备距离保持恒定的路径进行搜索，目标设备为第一设备或者第二设备；
选择模块，用于将搜索路径中位于双直视区域且取得整体目标函数值最大的位置点确定为无人机的中继服务位置。
第三方面，本发明实施例提供一种中继无人机，包括：动力系统、无线通信装置、至少一个处理器和存储器；
动力系统用于向无人机提供飞行动力；
无线通信装置用于向第一设备和第二设备提供中继服务；
存储器存储计算机执行指令；
至少一个处理器执行存储器存储的计算机执行指令，使得至少一个处理器执行如上述任一实施例提供的无人机中继服务位置的确定方法。
第四方面，本发明实施例提供一种计算机可读存储介质，所述计算机可读存储介质中存储有计算机执行指令，计算机执行指令被处理器执行时用于实现如上述任一实施例提供的无人机中继服务位置的确定方法。
本发明实施例提供的无人机中继服务位置的确定方法与装置，首先在搜索垂面中确定搜索起始位置点，搜索起始位置点与第一设备和第二设备之间的链路均为直视链路，搜索垂面为垂直于地面且分隔第一设备和第二设备的平面或者柱面；然后以搜索起始位置点作为搜索起点，分别在第一区域和第二区域中进行位置搜索直至高度降低至无人机的最小飞行高度，第一区域和第二区域由经搜索起始位置点且与地面垂直的直线将搜索垂面划分而成，位置搜索包括：若位于双直视区域，则在搜索垂面中垂直向下进行搜索以增大目标函数的取值；若位于非双直视区域，则在搜索垂面中沿着到目标设备距离保持恒定的路径进行搜索，目标设备为第一设备或者第二设备；最后将搜索路径中位于双直视区域且取得整体目标函数值最大的位置点确定为无人机的中继服务位置。通过合理设置搜索起始点，并且针对双直视区域和非双直视区域分别制定搜索策略，实现了在线性搜索复杂度情况下，找到近似全局最优的无人机中继服务位置，在追求最优性能的目标上极大地降低了搜索复杂度。
附图说明
图1为本发明一实施例提供的应用场景示意图；
图2为本发明一实施例提供的直视链路和非直视链路的示意图；
图3为本发明一实施例提供的坐标系示意图；
图4为本发明提供的无人机中继服务位置的确定方法一实施例的流程图；
图5为本发明一实施例提供的线性搜索垂面和弧形搜索垂面的示意图；
图6为本发明一实施例提供的吞吐量仿真对比示意图；
图7为本发明一实施例提供的搜索轨迹示意图；
图8为本发明提供的无人机中继服务位置的确定装置一实施例的结构示意图；
图9为本发明提供的中继无人机一实施例的结构示意图。
具体实施方式
下面通过具体实施方式结合附图对本发明作进一步详细说明。其中不同实施方式中类似元件采用了相关联的类似的元件标号。在以下的实施方式中，很多细节描述是为了使得本申请能被更好的理解。然而，本领域技术人员可以毫不费力的认识到，其中部分特征在不同情况下是可以省略的，或者可以由其他元件、材料、方法所替代。在某些情况下，本申请相关的一些操作并没有在说明书中显示或者描述，这是为了避免本申请的核心部分被过多的描述所淹没，而对于本领域技术人员而言，详细描述这些相关操作并不是必要的，他们根据说明书中的描述以及本领域的一般技术知识即可完整了解相关操作。
另外，说明书中所描述的特点、操作或者特征可以以任意适当的方式结合形成各种实施方式。同时，方法描述中的各步骤或者动作也可以按照本领域技术人员所能显而易见的方式进行顺序调换或调整。因此，说明书和附图中的各种顺序只是为了清楚描述某一个实施例，并不意味着是必须的顺序，除非另有说明其中某个顺序是必须遵循的。
本文中为部件所编序号本身，例如“第一”、“第二”等，仅用于区分所描述的对象，不具有任何顺序或技术含义。而本申请所说“连接”、“联接”，如无特别说明，均包括直接和间接连接(联接)。
无人机具有灵活的移动性，适合用做中继，提供中继服务。无人机中继服务具有广阔的应用前景，因此近年来备受关注，例如可以采用无人机辅助通信，为通信受阻的两个通信设备提供中继服务以提高通信质量；在无线充电场景下，在两个设备间进行无线能量中转以提高无线充电的有效距离；在视频监控场景下，无人机对监控对象进行实时拍摄并将拍摄到的图像或者视频通过无线通信的方式实时回传至目标设备。无人机中继服务位置必然影响中继服务的质量，因此研究如何确定无人机中继服务位置具有重要的意义。
目前确定无人机中继服务位置的常用方法包括基于统计学模型的方法和射线追 踪的方法。其中，基于统计学模型的方法，其基本思路是基于地理统计信息，例如楼宇的高度和密度的统计分布等，根据空对地信道的空间几何参数，计算出链路被障碍物遮挡的概率，从而推导出无人机中继服务的最优位置。然而该方法只能从统计学的角度分析空对地链路的质量，无法针对一条确切的链路判断其被遮挡的状态，因此无法保证找到最优的无人机中继服务位置。射线追踪的方法需要借助城市的三维模型来计算空对地链路的质量，其依赖于及时、准确和精细的三维环境数据，包括建筑物的位置、结构细节和材料数据等。然而由于城市环境的发展与变迁日新月异，及时地维护一个准确和精细的三维环境数据成本巨大，通常是无线通信网络运营商无法承受的；即使获取到了准确和精细的三维环境数据，由于射线追踪的方法难以提供关于链路质量在空间上分布的结构化特征，因此基于该方法搜索无人机的最优中继服务位置时通常无规律可循，搜索量大、计算复杂度高且计算量极其巨大，难以在无人机这样的小型化平台上运行。综上所述，现有技术中确定无人机中继服务位置的方法尚有待改进。
为了解决上述方法中的至少一种问题，本申请提出一种无人机中继服务位置的确定方法与装置，通过合理设置搜索起始点，并且在无人机处于双直视区域时，垂直向下进行搜索以便快速地降低高度从而增大目标函数的取值；在无人机处于非双直视区域时，沿着到目标设备的距离保持恒定的路径进行搜索。例如可以沿着等势面进行搜索，以使目标函数的取值不减小。本申请中的目标函数包括但不限于链路容量函数、链路数据传输速率函数、链路数据传输准确率函数和视频图像质量函数等。无人机用于向第一设备和第二设备提供中继服务时，双直视区域为无人机与第一设备和第二设备之间的链路均为直视链路(Line-of-Sight，LoS)的区域，非双直视区域为无人机与第一设备和第二设备之间的链路至少有一条为非直视链路(Non-Line-of-Sight，NLoS)的区域，即包括了无人机与第一设备和第二设备之间的链路均为非直视链路的区域，以及无人机与第一设备和第二设备之间有一条直视链路和一条非直视链路的区域。本申请提供的方法可以在线性搜索复杂度情况下，找到近似全局最优的无人机中继服务位置。下面将通过具体的实施例来进行详细说明。
本申请提供的无人机中继服务位置的确定方法可以应用于无人机。图1为本发明一实施例提供的应用场景示意图。如图1所示，当第一设备102和第二设备103之间的无线通信链路由于受到周围建筑物遮挡而无法达到通信服务质量要求时，可以采用无人机101作为中继站，为第一设备102和第二设备103提供信号中继服务。需要说明的是，第一设备102和第二设备103既可以是两个移动终端，也可以是一个移动终端和一个地面基站；第一设备102和第二设备103还可以是聚集在两个局部区域中的多个移动终端，如图1所示，第一设备102可以是第一设备102所在椭圆区域中的全部或者部分移动终端，第二设备103可以是第二设备103所在椭圆区 域中的全部或者部分移动设备。
为了保障无人机的安全性，将无人机的高度限定在[H min，H max]。其中，H min为无人机的最小飞行高度，H max为无人机的最大飞行高度。可以理解的是，一方面为了避免无人机与搜索区域中的障碍物发生碰撞以保证无人机的飞行安全，另一方面为了提高搜索效率，无人机的最小飞行高度H min大于搜索区域中障碍物的最大高度。例如大于第一设备102和第二设备103相关区域中障碍物的最大高度。
虽然无人机在一个相对较高的高度上飞行，但是无人机与设备之间的链路依然可能被障碍物例如建筑物、树木和高山等阻挡。将被障碍物阻挡的链路称为非直视链路(Non-Line-of-Sight，NLoS)，相反的，将未被障碍物阻挡的链路称为直视链路(Line-of-Sight，LoS)。如图2所示，无人机101与第一设备102之间的链路未受到障碍物的阻挡，为直视链路；无人机101与第二设备103之间的链路被建筑物阻挡，为非直视链路。可以理解的是，相同条件下LoS链路的性能要优于NLoS链路。例如相同距离下，LoS链路的链路容量、数据传输速率和数据传输准确率都要高于NLoS链路。毫米波通信、无线光通信等都对障碍物较为敏感，障碍物的遮蔽会大大降低通信质量，而监控服务中则要求必须是LoS链路，因此本实施例致力于使无人机至两个设备的链路均为LoS链路。为便于描述，将无人机与两个设备之间的链路均为LoS链路的区域称为双直视区域，将其他区域即无人机与两个设备之间的链路均为NLoS链路的区域，以及无人机与两个设备之间有一条LoS链路和一条NLoS链路的区域称为非双直视区域。
如果无人机在某位置处与设备之间的链路为无遮挡的LoS链路，那么在该位置正上方的所有位置上无人机与设备之间的链路均为无遮挡的LoS链路；如果无人机在某位置处与设备之间的链路为有遮挡的NLoS链路，那么在该位置正下方的所有位置上无人机与设备之间的链路均为有遮挡的NLoS链路。当无人机用于向第一设备和第二设备提供中继服务时，如果无人机在某位置上处于双直视区域，那么在该位置正上方的所有位置上无人机均处于双直视区域；如果无人机在某位置上处于非双直视区域，那么在该位置正下方的所有位置上无人机均处于非双直视区域。
下面以目标函数为链路容量函数为例进行说明，目标函数为链路数据传输速率函数、链路数据传输准确率函数等其他函数时可以参考目标函数为链路容量函数的情况。本发明实施例提供的无人机中继服务位置的确定方法适用于链路容量与距离负相关的情况，也就是说，当无人机与设备之间的距离增大时，无人机与设备之间的链路容量减小，例如适用于如下链路容量模型：
f(d(x))＝log 2(1+kh(d(x)))；
h(d(x))＝b-a lg(d(x))；
其中，x为无人机的三维空间位置，d(x)为无人机到设备的距离，k、b和a是与 通信链路变量相关的参数，具体的，与发射功率、信道状况、噪声状况和链路遮蔽状况等相关，对于不同的通信链路，上述参数不同。d(x)为无人机与设备之间的距离，f(x)为链路容量。因此为了提升中继服务性能，无人机应该尽可能降低高度并且靠近第一设备和第二设备。
在无人机提供中继服务的场景下，最差通信链路的链路容量将成为系统的通信瓶颈，因此无人机的最佳中继服务位置应使最差通信链路的链路容量最大化，也即最大化“瓶颈链路容量”F(x)。这里的瓶颈链路容量具体定义为F(x)＝min{f(d 1(x)),f(d 2(x))}，其中，d 1(x)＝‖x-u 1‖，d 2(x)＝‖x-u 2‖，它们分别为无人机到第一设备的距离和无人机到第二设备的距离。
在三维空间中，若所有无人机可选位置都处于双直视区域，无人机的最佳中继服务位置位于无人机与两个设备之间的通信链路容量相等的等势面上。等势面是由到两个用户设备的链路容量值相等的点形成的。设第一设备的位置为u 1＝(u 11,u 12,u 13)，第二设备的位置为u 2＝(u 21,u 22,u 23)，无人机的位置为x＝(x 1,x 2,x 3)。设无人机与第一设备的链路函数值为f 1(d 1(x))，无人机与第二设备的链路函数值为f 2(d 2(x))，其中d 1(x)＝‖x-u 1‖，d 2(x)＝‖x-u 2‖，它们分别为无人机到第一设备的距离和无人机到第二设备的距离。则等势面可表示为S{x:h(x)＝f 1(d 1(x))-f 2(d 2(x))＝0}。这个特征可用以下反例来说明。假设无人机的中继服务位置不满足与两个设备之间的通信链路容量相等，那么一定可以通过调整该位置，使得较优链路的链路容量下降，较差链路(瓶颈链路)的链路容量增加，从而达到比之前位置更好的通信效果，直至无人机与两个设备之间的通信链路容量相等。例如无人机与第一设备之间的链路容量f(d 1(x))大于无人机与第二设备之间的链路容量f(d 2(x))，那么在三维空间中，无人机一定可以找到一个移动方向使得无人机与第二设备之间的距离缩小，相应的无人机与第二设备之间的链路容量f(d 2(x))增大。与此同时，该方向可能会增加或者减小无人机与第一设备之间的链路容量f(d 1(x))，但是只要依然满足f(d 1(x))>f(d 2(x))(如沿该方向移动足够小的距离)，那么沿着该方向的移动一定会增加系统的通信链路容量。
无人机的最佳中继服务位置在双直视区域与非双直视区域的边界上。为便于描述，建立如图3所示的坐标系。该坐标系以第一设备所在位置u 1作为坐标原点O，沿着第一设备所在位置u 1与第二设备所在位置u 2的连线确定y轴，xOy平面由水平面确定，x轴穿过第一设备所在位置u 1，z轴垂直于xOy平面且穿过第一设备所在位置u 1。图3中的灰色平面用于表示平行于yOz平面的任一平面，灰色平面中的虚折线用于表示双直视区域与非双直视区域的边界，折线上方为双直视区域，折线下方为非双直视区域。假设无人机在该灰色平面中的最佳位置位于点p 2处，如图3所示，p 2并不在双直视区域与非双直视区域的边界上，p 2至第一设备的距离记为 d(p 2,u 1)＝||p 2-u 1|| 2，p 2至第二设备的距离记为d(p 2,u 2)＝||p 2-u 2|| 2。那么一定可以在双直视区域与非双直视区域的边界上找到一点p 1，p 1x＝p 2x，p 1y＝p 2y，且0<p 1z<p 2z，使得d(p 1,u 1)<d(p 2,u 1)且d(p 1,u 2)<d(p 2,u 2)。由于链路容量与距离负相关，所以p 1点的链路容量f(d 1(p 1))大于等于p 2点的链路容量f(d 1(p 2))，这与p 2为最佳位置点相矛盾。因此，无人机的最佳中继服务位置在双直视区域与非双直视区域的边界上。
在上述实施例提供的应用场景下，本发明还提供一种无人机中继服务位置的确定方法。请参考图4，图4为本发明提供的无人机中继服务位置的确定方法一实施例的流程图。如图4所示，本实施例提供的方法可以包括：
S101、在搜索垂面中确定搜索起始位置点，搜索起始位置点与第一设备和第二设备之间的链路均为直视链路，搜索垂面为垂直于地面且分隔第一设备和第二设备的平面或者柱面。
本实施例中选取垂直于地面且分隔第一设备和第二设备的平面或者柱面作为搜索垂面。并且通过上述实施例可知无人机的最佳中继服务位置位于双直视区域中，因此本实施例中选取与第一设备和第二设备之间的链路均为直视链路的位置点作为搜索起始位置点有助于减少搜索量，提高搜索效率。
本实施例中的搜索垂面可以是平面，也可以是柱面。请参考图5，图5中左侧所示为平面，即为线性搜索垂面，图5中右侧所示为柱面，即为弧形搜索垂面。一种可选的实施方式中，线性搜索垂面可以通过如下方法确定：将图5中第一设备的位置记为(u 11,u 12,0)，第二设备的位置记为(u 21,u 22,0)，最大飞行高度记为H max，最低飞行高度记为H min，定义直线l 1过点(u 11,u 12,H min)和(u 21,u 22,H min)，定义直线l 2过点(u 11,u 12,H max)和(u 21,u 22,H max)。将l 1与等势面的交点表示为h 1，将l 2与等势面的交点表示为h 2，将过h 1且垂直于地面的直线表示为l h1，将过h 2且垂直于地面的直线表示为l h2，则线性搜索垂面可以是l h1与l h2之间的垂直于地面且分隔第一设备和第二设备的的任一平面。
一种可选的实施方式中，可以采用如下方式在搜索垂面中确定搜索起始位置点包括：
在搜索垂面中从无人机的最小飞行高度向上搜索，若达到无人机的最大飞行高度，则在搜索垂面中向两侧搜索，直至在搜索垂面中找到与第一设备和第二设备之间的链路均为直视链路的位置点，确定为搜索起始位置点；
或者，
从第一设备正上方最大飞行高度处向第二设备正上方最大飞行高度处，或者，从第二设备正上方最大飞行高度处向第一设备正上方最大飞行高度处搜索，直至到达搜索垂面，若此时无人机与第一设备和第二设备之间的链路均为直视链路，则将 该位置点确定为搜索起始位置点；反之，则在搜索垂面中向两侧搜索，直至在搜索垂面中找到与第一设备和第二设备之间的链路均为直视链路的位置点，确定为搜索起始位置点。
S102、以搜索起始位置点作为搜索起点，分别在第一区域和第二区域中进行位置搜索直至高度降低至无人机的最小飞行高度，第一区域和第二区域由经搜索起始位置点且与地面垂直的直线将搜索垂面划分而成，位置搜索包括：若位于双直视区域，则在搜索垂面中垂直向下进行搜索以增大目标函数的取值；若位于非双直视区域，则在搜索垂面中沿着到目标设备距离保持恒定的路径进行搜索，目标设备为第一设备或者第二设备。
本实施例中由经搜索起始位置点且与地面垂直的直线将搜索垂面划分为第一区域和第二区域，分别在两个区域中进行位置搜索，既可以提高搜索效率，也可以避免沿着单一方向进行搜索而错过最佳位置。当无人机位于双直视区域时，无人机与第一设备和第二设备之间的链路均为LoS链路，此时在搜索垂面中垂直向下进行搜索，减小无人机与第一设备和第二设备之间的距离，由于目标函数与距离负相关，因此沿该方向进行搜索可以增大目标函数的取值。当无人机位于非双直视区域时，则在搜索垂面中沿着到目标设备距离保持恒定的路径进行搜索，以使无人机与目标设备之间的目标函数取值不减小。
一种可选的实施方式中，可以采用如下方式确定目标设备：若当前位置到第一设备的目标函数的取值小于当前位置到第二设备的目标函数的取值，则目标设备为第一设备；若当前位置到第一设备的目标函数的取值大于等于当前位置到第二设备的目标函数的取值，则目标设备为第二设备；若当前位置到第一设备的目标函数的取值等于当前位置到第二设备的目标函数的取值，则目标设备为第一设备和第二设备中的任意一个。选择目标函数取值小的设备作为目标设备，有助于提高搜索路径上的整体目标函数值。整体目标函数可以理解为链路的瓶颈目标函数值，由无人机与第一设备的目标函数和无人机与第二设备的目标函数中取值较小的确定。
为便于选择最佳的中继服务位置，可以预先对搜索路径上各个位置处目标函数的取值进行存储。需要说明的是，为了避免无人机与搜索区域中的障碍物发生碰撞，本实施例中无人机的最小飞行高度需大于第一设备和第二设备相关区域中障碍物的最大高度以保证无人机的飞行安全。
S103、将搜索路径中位于双直视区域且取得整体目标函数值最大的位置点确定为无人机的中继服务位置。
本实施例中在完成第一区域和第二区域中的位置搜索之后，将搜索路径中位于双直视区域且取得整体目标函数值最大的位置点确定为无人机的中继服务位置。整体目标函数值由无人机与第一设备的目标函数取值和无人机与第二设备的目标函数 取值中较小的确定。目标函数取值可以通过无人机与第一设备和第二设备之间的无线通信进行测定，本实施例并不限定具体的实施方式。
无人机中继服务的最优位置是受周围环境的遮挡情况影响的，而周围环境的遮挡情况是由地形决定的，而地形通常没有规律可循，比如建筑物、植被等可能出现在任意位置，具有几乎任意的高度。也就是说，在无人机中继服务位置的最优化问题中是没有有利特征可以使用的。而三维空间中的最优化问题，在没有有利特征的情况下，通用需要3次方搜索复杂度。以目标区域半径为L为例，则需要O(L 3)的搜索路径长度才能找到最优位置。而本实施例提供的方法可以在线性搜索复杂度的情况下，找到近似全局最优的无人机中继服务位置。同样对于半径为L的目标区域，在最坏的情况下，本实施例提供的方法只需要搜索kL长度即可，其中k为一个与L无关的常数。以需要提供中继服务的地面用户位于一个面积为64万平方米的目标区域内为例，按照本发明实施例提供的方法搜索路径长度约为400米，而如果采用遍历二维平面的穷举式搜索，搜索路径长度约为100km，采用遍历三维空间的穷举式搜索，搜索路径长度约为3000km，其中，最低飞行高度设定约为50m，最大高度设定约为200m。
本发明实施例提供的方法虽然仅具有线性搜索复杂度，但是依然可以找到近似全局最优的无人机中继服务位置。为了直观地展示本申请所获得的性能增益，申请人以图1所示无人机为两个终端设备提供中继通信服务的应用场景为例，通过仿真对多种不同方法的通信吞吐量进行了模拟，仿真结果请参考图6。如图6所示，本发明实施例提供的方法与三维穷举法的性能已经相当接近，相比于传统的统计学方法更是能够带来巨大的性能增益。为便于对各种方法的性能进行比较，对于各种方法的平均吞吐量进行了统计，如表1所示，其中，Hc为无人机的最大飞行高度与最小飞行高度的平均值。
表1
方法名称 平均吞吐量(Gbps)
统计学方法 4.19
二维穷举法(H＝200m) 6.40
二维穷举法(H＝100m) 6.84
二维穷举法(H＝Hc) 6.80
本申请方法 7.50
三维穷举法 7.53
本实施例提供的无人机中继服务位置的确定方法，首先在搜索垂面中确定搜索 起始位置点；然后以搜索起始位置点作为搜索起点，分别在第一区域和第二区域中进行位置搜索，位置搜索包括：若位于双直视区域，则在搜索垂面中垂直向下进行搜索以增大目标函数的取值；若位于非双直视区域，则在搜索垂面中沿着到目标设备距离保持恒定的路径进行搜索；最后将搜索路径中位于双直视区域且取得整体目标函数值最大的位置点确定为无人机的中继服务位置。通过合理设置搜索起始点，并且针对双直视区域和非双直视区域分别制定搜索策略，实现了在线性搜索复杂度情况下，找到近似全局最优的无人机中继服务位置，在追求最优性能的目标上极大地降低了搜索复杂度。
如图1所示的应用场景，无人机用于向第一设备和第二设备提供中继服务，当第一设备和第二设备处于相同的高度，具有相似的通信条件(例如具有相似的发射功率、天线增益和其他通信参数)时，满足对称性条件。也就是说，从无人机的视角来看，第一设备和第二设备是对称的。此时最佳中继服务位置位于至第一设备和第二设备距离相等的中垂面上。中垂面是经过第一设备和第二设备连线中点的搜索垂面。在上述实施例的基础上，下面将针对满足对称性条件时如何确定无人机的中继服务位置进行详细说明。
一种可选的实施方式中，当第一设备和第二设备满足对称性条件时，搜索垂面为经过第一设备和第二设备连线的中点的中垂面；第一区域和第二区域由经搜索起始位置点且与地面垂直的直线将中垂面划分而成。具体的，位置搜索可以包括：若位于双直视区域，则在中垂面中垂直向下进行位置搜索；若位于非双直视区域，则在中垂面中以第一设备和第二设备的中点为圆心，以当前位置至圆心的距离为半径的圆弧上，沿着远离搜索起始位置点的方向进行位置搜索。
一种可选的实施方式中，当第一设备和第二设备不满足对称性条件时，搜索垂面为分隔第一设备和第二设备的平面或柱面，平面或柱面上存在一条曲线，曲线上每一位置点到第一设备的目标函数值等于该位置点到第二设备的目标函数值。
请参考图7，图7为本发明一实施例提供的满足对称性条件时在中垂面上进行搜索的搜索轨迹示意图。图7所示平面为第一设备和第二设备的中垂面的正视图。其中H max为无人机的最大飞行高度，H min为无人机的最小飞行高度。在中垂面上选取坐标为(
Figure PCTCN2022131915-appb-000001
H max)的点作为搜索起始位置点，如图7中所示p (0)点即为搜索起始位置点。其中u 1x为第一设备的横坐标，u 1y为第一设备的纵坐标，u 2x为第二设备的横坐标，u 2y为第二设备的纵坐标。在确定搜索起始位置点之后，分别在左半区(即第一区域)和右半区(即第二区域)进行搜索，左半区和右半区是由经搜索起始位置点且与地面垂直的直线将中垂面划分而成的。
在上述实施例的基础上，为了避免错过最佳中继服务位置，在第一区域和第二 区域中进行位置搜索之前，还需要分别确定第一区域和第二区域的起点。具体的，若搜索起始位置点位于双直视区域，则搜索起始位置点为第一区域和第二区域的起点；若搜索起始位置点位于非双直视区域，则以搜索起始位置点作为搜索起点，分别在第一区域和第二区域中沿着高度为无人机的最大飞行高度的直线逐步搜索，将第一区域中搜索到的第一个位于双直视区域的位置点作为第一区域的起点，将第二区域中搜索到的第一个位于双直视区域的位置点作为第二区域的起点或将第一区域中搜索起始点正下方某一点作为第二区域的搜索起点，该点与目标设备的距离需大于等于第一区域搜索到的最后一点与目标设备的距离。参考图7中沿高度为H max的直线的搜索轨迹，在第一区域中搜索一段距离之后，找到第一个位于双直视区域的位置点
Figure PCTCN2022131915-appb-000002
则
Figure PCTCN2022131915-appb-000003
为第一区域的起点；在第二区域中将第一区域中搜索起始点正下方的某一点作为第二区域的起点，该点与目标设备的距离等于第一区域搜索到的最后一点与目标设备的距离。
然后分别从第一区域和第二区域的起点开始，在两个区域内按照如下方法进行位置搜索：若位于双直视区域，则在中垂面中垂直向下进行位置搜索，即保持x轴和y轴坐标不变，z轴坐标减小；若位于非双直视区域，则在中垂面中以第一设备和第二设备的中点为圆心，以当前位置至圆心的距离为半径的圆弧上，沿着远离搜索起始位置点的方向进行位置搜索。即沿着图7中圆弧朝向高度减小的方向搜索，由于在圆弧上移动时，无人机与第一设备和第二设备之间的距离保持不变，因此沿着圆弧进行搜索不会使链路容量减小。最后将第一区域和第二区域搜索轨迹上整体目标函数值最大的位置点确定为无人机的中继服务位置，即图7中左边区域标有五角星的位置点为无人机的中继服务位置。
图8为本发明提供的无人机中继服务位置的确定装置一实施例的结构示意图。如图8所示，本实施例提供的无人机中继服务位置的确定装置80可以包括：确定模块801、搜索模块802和选择模块803。
确定模块801，用于用于在搜索垂面中确定搜索起始位置点，搜索起始位置点与第一设备和第二设备之间的链路均为直视链路，搜索垂面为垂直于地面且垂分隔第一设备和第二设备的平面或者柱面。
搜索模块802，用于以搜索起始位置点作为搜索起点，分别在第一区域和第二区域中进行位置搜索直至高度降低至无人机的最小飞行高度，第一区域和第二区域由经搜索起始位置点且与地面垂直的直线将搜索垂面划分而成，位置搜索包括：若位于双直视区域，则在搜索垂面中垂直向下进行搜索以增大目标函数的取值；若位于非双直视区域，则在搜索垂面中沿着到目标设备距离保持恒定的路径进行搜索，目标设备为第一设备或者第二设备。
选择模块803，用于将搜索路径中位于双直视区域且取得整体目标函数值最大的 位置点确定为无人机的中继服务位置。
本实施例提供的无人机中继服务位置的确定装置可用于执行图4对应的方法实施例的技术方案，其实现原理和技术效果类似，此处不再赘述。
可选的，若当前位置到第一设备的目标函数的取值小于当前位置到第二设备的目标函数的取值，则目标设备为第一设备；若当前位置到第一设备的目标函数的取值大于等于当前位置到第二设备的目标函数的取值，则目标设备为第二设备。
可选的，确定模块801用于在搜索垂面中确定搜索起始位置点具体可以包括：
在搜索垂面中从无人机的最小飞行高度向上搜索，若达到无人机的最大飞行高度，则在搜索垂面中向两侧搜索，直至在搜索垂面中找到与第一设备和第二设备之间的链路均为直视链路的位置点，确定为搜索起始位置点；
或者，
从第一设备正上方最大飞行高度处向第二设备正上方最大飞行高度处，或者，从第二设备正上方最大飞行高度处向第一设备正上方最大飞行高度处搜索，直至到达搜索垂面，若此时无人机与第一设备和第二设备之间的链路均为直视链路，则将该位置点确定为搜索起始位置点；反之，则在搜索垂面中向两侧搜索，直至在搜索垂面中找到与第一设备和第二设备之间的链路均为直视链路的位置点，确定为搜索起始位置点。
可选的，当第一设备和第二设备满足对称性条件时，搜索垂面为经过第一设备和第二设备连线的中点的中垂面；第一区域和第二区域由经搜索起始位置点且与地面垂直的直线将中垂面划分而成。
可选的，搜索模块802还用于若位于双直视区域，则在中垂面中垂直向下进行位置搜索；若位于非双直视区域，则在中垂面中以第一设备和第二设备的中点为圆心，以当前位置至圆心的距离为半径的圆弧上，沿着远离搜索起始位置点的方向进行位置搜索。
可选的，目标函数包括链路容量函数、链路数据传输速率函数、链路数据传输准确率函数和视频图像质量函数。
可选的，无人机的最小飞行高度大于第一设备和第二设备相关区域中障碍物的最大高度。
可选的，当第一设备和第二设备不满足对称性条件时，搜索垂面为分隔第一设备和第二设备的平面或柱面，平面或柱面上存在一条曲线，曲线上每一位置点到第一设备的目标函数值等于该位置点到第二设备的目标函数值。
本发明实施例还提供一种中继无人机。图9为本发明提供的中继无人机一实施例的结构示意图。如图9所示，本实施例提供的中继无人机90可以包括：动力系统901、无线通信装置902、至少一个处理器903和存储器904，各元件之间通过总线 905连接。
其中，动力系统901用于向无人机提供飞行动力；无线通信装置902用于向第一设备和第二设备提供中继服务；存储器904存储计算机执行指令；至少一个处理器903执行存储器存储的计算机执行指令，使得至少一个处理器903执行如上述任一实施例提供的无人机中继服务位置的确定方法。
存储器904可以是，但不限于，随机存取存储器(Random Access Memory，简称：RAM)，只读存储器(Read Only Memory，简称：ROM)，可编程只读存储器(Programmable Read-Only Memory，简称：PROM)，可擦除只读存储器(Erasable Programmable Read-Only Memory，简称：EPROM)，电可擦除只读存储器(Electric Erasable Programmable Read-Only Memory，简称：EEPROM)等。其中，存储器904用于存储程序，处理器903在接收到执行指令后，执行程序。进一步地，上述存储器904内的软件程序以及模块还可包括操作系统，其可包括各种用于管理系统任务(例如内存管理、存储设备控制、电源管理等)的软件组件和/或驱动，并可与各种硬件或软件组件相互通信，从而提供其他软件组件的运行环境。
处理器903可以是一种集成电路芯片，具有信号的处理能力。上述的处理器903可以是通用处理器，包括中央处理器(Central Processing Unit，简称：CPU)、网络处理器(Network Processor，简称：NP)等。可以实现或者执行本发明实施例中的公开的各方法、步骤及逻辑框图。通用处理器可以是微处理器或者该处理器也可以是任何常规的处理器等。可以理解，图9的结构仅为示意，还可以包括比图9中所示更多或者更少的组件，或者具有与图9所示不同的配置。图9中所示的各组件可以采用硬件和/或软件实现。
本文参照了各种示范实施例进行说明。然而，本领域的技术人员将认识到，在不脱离本文范围的情况下，可以对示范性实施例做出改变和修正。例如，各种操作步骤以及用于执行操作步骤的组件，可以根据特定的应用或考虑与系统的操作相关联的任何数量的成本函数以不同的方式实现(例如一个或多个步骤可以被删除、修改或结合到其他步骤中)。
另外，如本领域技术人员所理解的，本文的原理可以反映在计算机可读存储介质上的计算机程序产品中，该可读存储介质预装有计算机可读程序代码。任何有形的、非暂时性的计算机可读存储介质皆可被使用，包括磁存储设备(硬盘、软盘等)、光学存储设备(CD-ROM、DVD、Blu Ray盘等)、闪存和/或诸如此类。这些计算机程序指令可被加载到通用计算机、专用计算机或其他可编程数据处理设备上以形成机器，使得这些在计算机上或其他可编程数据处理装置上执行的指令可以生成实现指定的功能的装置。这些计算机程序指令也可以存储在计算机可读存储器中，该计算机可读存储器可以指示计算机或其他可编程数据处理设备以特定的方式运行，这 样存储在计算机可读存储器中的指令就可以形成一件制造品，包括实现指定功能的实现装置。计算机程序指令也可以加载到计算机或其他可编程数据处理设备上，从而在计算机或其他可编程设备上执行一系列操作步骤以产生一个计算机实现的进程，使得在计算机或其他可编程设备上执行的指令可以提供用于实现指定功能的步骤。
以上应用了具体个例对本发明进行阐述，只是用于帮助理解本发明，并不用以限制本发明。对于本发明所属技术领域的技术人员，依据本发明的思想，还可以做出若干简单推演、变形或替换。

Claims (7)

  1. 一种无人机中继服务位置的确定方法，所述无人机用于向第一设备和第二设备提供中继服务，其特征在于，所述方法包括：
    在搜索垂面中确定搜索起始位置点，所述搜索起始位置点与所述第一设备和所述第二设备之间的链路均为直视链路，所述搜索垂面为垂直于地面且分隔所述第一设备和所述第二设备的平面或者柱面；
    以所述搜索起始位置点作为搜索起点，分别在第一区域和第二区域中进行位置搜索直至高度降低至所述无人机的最小飞行高度，所述第一区域和所述第二区域由经所述搜索起始位置点且与地面垂直的直线将所述搜索垂面划分而成，所述位置搜索包括：若位于双直视区域，则在所述搜索垂面中垂直向下进行搜索以增大目标函数的取值；若位于非双直视区域，则在所述搜索垂面中沿着到目标设备距离保持恒定的路径进行搜索，所述目标设备为所述第一设备或者所述第二设备；
    将搜索路径中位于双直视区域且取得整体目标函数值最大的位置点确定为所述无人机的中继服务位置；
    当第一设备和第二设备满足对称性条件时，搜索垂面为经过第一设备和第二设备连线的中点的中垂面；第一区域和第二区域由经搜索起始位置点且与地面垂直的直线将中垂面划分而成；所述位置搜索包括：若位于双直视区域，则在中垂面中垂直向下进行位置搜索；若位于非双直视区域，则在中垂面中以第一设备和第二设备的中点为圆心，以当前位置至圆心的距离为半径的圆弧上，沿着远离搜索起始位置点的方向进行位置搜索；将第一区域和第二区域搜索轨迹上整体目标函数值最大的位置点确定为无人机的中继服务位置；
    其中，所述在中垂面中垂直向下进行位置搜索包括：保持x轴和y轴坐标不变，z轴坐标减小的方向进行位置搜索；所述以当前位置至圆心的距离为半径的圆弧上，沿着远离搜索起始位置点的方向进行位置搜索包括：沿着圆弧朝向高度减小的方向进行位置搜索；
    当第一设备和第二设备不满足对称性条件时，搜索垂面为分隔第一设备和第二设备的平面或柱面，平面或柱面上存在一条曲线，曲线上每一位置点到第一设备的目标函数值等于该位置点到第二设备的目标函数值。
  2. 如权利要求1所述的方法，其特征在于，若当前位置到所述第一设备的目标函数的取值小于当前位置到所述第二设备的目标函数的取值，则所述目标设备为所述第一设备；若当前位置到所述第一设备的目标函数的取值大于等于当前位置到所述第二设备的目标函数的取值，则所述目标设备为所述第二设备。
  3. 如权利要求1所述的方法，其特征在于，所述在搜索垂面中确定搜索起始 位置点包括：
    在所述搜索垂面中从所述无人机的最小飞行高度向上搜索，若达到所述无人机的最大飞行高度，则在所述搜索垂面中向两侧搜索，直至在所述搜索垂面中找到与所述第一设备和所述第二设备之间的链路均为直视链路的位置点，确定为所述搜索起始位置点；
    或者，
    从所述第一设备正上方最大飞行高度处向所述第二设备正上方最大飞行高度处，或者，从所述第二设备正上方最大飞行高度处向所述第一设备正上方最大飞行高度处搜索，直至到达所述搜索垂面，若此时所述无人机与所述第一设备和所述第二设备之间的链路均为直视链路，则将该位置点确定为所述搜索起始位置点；反之，则在所述搜索垂面中向两侧搜索，直至在所述搜索垂面中找到与所述第一设备和所述第二设备之间的链路均为直视链路的位置点，确定为所述搜索起始位置点。
  4. 如权利要求1-3任一项所述的方法，其特征在于，所述目标函数包括链路容量函数、链路数据传输速率函数、链路数据传输准确率函数和视频图像质量函数。
  5. 一种无人机中继服务位置的确定装置，所述无人机用于向第一设备和第二设备提供中继服务，其特征在于，包括：
    确定模块，用于在搜索垂面中确定搜索起始位置点，所述搜索起始位置点与所述第一设备和所述第二设备之间的链路均为直视链路，所述搜索垂面为垂直于地面且分隔所述第一设备和所述第二设备的平面或者柱面；
    搜索模块，用于以所述搜索起始位置点作为搜索起点，分别在第一区域和第二区域中进行位置搜索直至高度降低至所述无人机的最小飞行高度，所述第一区域和所述第二区域由经所述搜索起始位置点且与地面垂直的直线将所述搜索垂面划分而成，所述位置搜索包括：若位于双直视区域，则在所述搜索垂面中垂直向下进行搜索以增大目标函数的取值；若位于非双直视区域，则在所述搜索垂面中沿着到目标设备距离保持恒定的路径进行搜索，所述目标设备为所述第一设备或者所述第二设备；
    选择模块，用于将搜索路径中位于双直视区域且取得整体目标函数值最大的位置点确定为所述无人机的中继服务位置；
    当第一设备和第二设备满足对称性条件时，搜索垂面为经过第一设备和第二设备连线的中点的中垂面；第一区域和第二区域由经搜索起始位置点且与地面垂直的直线将中垂面划分而成；所述位置搜索包括：若位于双直视区域，则在中垂面中垂直向下进行位置搜索；若位于非双直视区域，则在中垂面中以第一设备和第二设备的中点为圆心，以当前位置至圆心的距离为半径的圆弧上，沿着远离搜索起始位置点的方向进行位置搜索；将第一区域和第二区域搜索轨迹上整体目标函数值最大的 位置点确定为无人机的中继服务位置；
    其中，所述在中垂面中垂直向下进行位置搜索包括：保持x轴和y轴坐标不变，z轴坐标减小的方向进行位置搜索；所述以当前位置至圆心的距离为半径的圆弧上，沿着远离搜索起始位置点的方向进行位置搜索包括：沿着圆弧朝向高度减小的方向进行位置搜索；
    当第一设备和第二设备不满足对称性条件时，搜索垂面为分隔第一设备和第二设备的平面或柱面，平面或柱面上存在一条曲线，曲线上每一位置点到第一设备的目标函数值等于该位置点到第二设备的目标函数值。
  6. 一种中继无人机，其特征在于，包括：动力系统、无线通信装置、至少一个处理器和存储器；
    所述动力系统用于向所述无人机提供飞行动力；
    所述无线通信装置用于向第一设备和第二设备提供中继服务；
    所述存储器存储计算机执行指令；
    所述至少一个处理器执行所述存储器存储的计算机执行指令，使得所述至少一个处理器执行如权利要求1-4任一项所述的无人机中继服务位置的确定方法。
  7. 一种计算机可读存储介质，其特征在于，所述计算机可读存储介质中存储有计算机执行指令，所述计算机执行指令被处理器执行时用于实现如权利要求1-4任一项所述的无人机中继服务位置的确定方法。
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