Beam switching method and device, composite antenna system and computer equipment

Abstract

The invention relates to a beam switching method and device, a composite antenna system, computer equipment, a computer readable storage medium and a computer program product. The method comprises the following steps: monitoring a motion track of the low-altitude terminal; determining beam switching time of the low-altitude terminal under a composite antenna according to the motion trail of the low-altitude terminal; the composite antenna comprises an air antenna and a ground antenna, and an antenna backboard is arranged between the air antenna and the ground antenna; controlling the low-altitude terminal to perform beam switching according to the beam switching time; the beam switching means that the to-air beam of the to-air antenna is switched to the to-ground beam of the to-ground antenna, or the to-ground beam of the to-ground antenna is switched to the to-air beam of the to-air antenna. By adopting the method, the stability of beam switching can be improved.

Description

Technical Field

[0001] The present application relates to the field of mobile communication technology, and in particular to a beam switching method, device, composite antenna system, computer equipment, computer-readable storage medium and computer program product. Background Art

[0002] In the scenario where low-altitude communication networks and ground communication networks are jointly networked, low-altitude terminals (such as drones) are not only used for logistics distribution, but also for meteorological monitoring, agricultural monitoring, emergency communications, rescue operations, etc.

[0003] In traditional technology, low-altitude communication networks use existing ground communication networks to achieve compatible coverage of ground users and low-altitude users by adjusting the downtilt angle of ground base station antennas. However, the characteristics and requirements of air and ground coverage are different, and the isolation between them is not high enough, which will cause mutual interference between air and ground signals, especially in high-density areas, resulting in low-altitude terminals taking off from the ground or landing. When the beam is switched, it is not smooth enough, which leads to low stability of beam switching. Summary of the invention

[0004] Based on this, it is necessary to provide a beam switching method, device, composite antenna system, computer equipment, computer-readable storage medium and computer program product that can improve the smoothness of beam switching in response to the above technical problems.

[0005] In a first aspect, the present application provides a beam switching method, which is applied to a processing unit, including:

[0006] Monitor the movement trajectory of low-altitude terminals;

[0007] According to the motion trajectory of the low-altitude terminal, determining the beam switching time of the low-altitude terminal under the composite antenna; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna;

[0008] According to the beam switching time, the low-altitude terminal is controlled to perform beam switching; the beam switching means switching from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, or switching from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna.

[0009] In one embodiment, determining the beam switching time of the low-altitude terminal under the composite antenna according to the motion trajectory of the low-altitude terminal includes:

[0010] Predicting the take-off time or landing time of the low-altitude terminal according to the motion trajectory of the low-altitude terminal;

[0011] The take-off time or landing time of the low-altitude terminal is used as the beam switching time of the low-altitude terminal under the composite antenna.

[0012] In one of the embodiments, controlling the low-altitude terminal to perform beam switching according to the beam switching time includes:

[0013] When it is identified according to the motion trajectory that the low-altitude terminal is in a state of waiting to take off, the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna are jointly adjusted according to the beam switching time, so that the low-altitude terminal switches from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna;

[0014] When it is identified according to the motion trajectory that the low-altitude terminal is in a state of waiting to land, the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna are jointly adjusted according to the beam switching time, so that the low-altitude terminal switches from the air-to-air beam of the air-to-air antenna to the ground beam of the ground-to-ground antenna.

[0015] In one of the embodiments, when the low-altitude terminal switches from the ground beam of the ground-to-ground antenna to the air beam of the air-to-air antenna, a first signal strength difference between the air beam and the ground beam is obtained;

[0016] According to the first signal strength difference, the beam direction and beam power of the air beam are adjusted so that the signal strength of the adjusted air beam reaches the signal strength of the ground beam.

[0017] In one of the embodiments, when the low-altitude terminal switches from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, a second signal strength difference between the ground-to-air beam and the air-to-air beam is obtained;

[0018] According to the second signal strength difference, the beam direction and beam power of the ground beam are adjusted so that the signal strength of the adjusted ground beam reaches the signal strength of the air beam.

[0019] In a second aspect, the present application also provides a composite antenna system, comprising: a composite antenna and a processing unit;

[0020] The composite antenna comprises an air-to-air antenna and a ground-to-ground antenna, and an antenna back plate is arranged between the air-to-air antenna and the ground-to-ground antenna;

[0021] The processing unit is used to execute the beam switching method described in any one of the embodiments of the first aspect.

[0022] In one embodiment, the air-to-air antenna is a circular curved three-dimensional antenna symmetrical around a central axis; the air-to-air antenna is arranged above the antenna back plate and is fixed to the antenna pole through the antenna back plate;

[0023] The ground-to-ground antenna is arranged below the antenna back plate and is fixed on the antenna pole through a support member.

[0024] In one of the embodiments, the number of the air-to-air antennas is 1, and the air-to-air antenna corresponds to one cell, so as to achieve all-round air coverage;

[0025] The number of the ground antennas is 3, each ground antenna corresponds to a cell, and the angle between each ground antenna is 120 degrees, so as to achieve all-round ground coverage.

[0026] In one of the embodiments, the ground-to-air antenna and the air-to-air antenna are of the same frequency and the same standard; or, the ground-to-air antenna and the air-to-air antenna are of the same frequency and different standards; or, the ground-to-air antenna and the air-to-air antenna are of different frequencies and the same standard; or, the ground-to-air antenna and the air-to-air antenna are of different frequencies and different standards.

[0027] In one of the embodiments, the ground-to-air antenna and the air-to-air antenna are both passive antennas; or, the ground-to-air antenna and the air-to-air antenna are both active antennas; or, the ground-to-air antenna is a passive antenna and the air-to-air antenna is an active antenna; or, the ground-to-air antenna is an active antenna and the air-to-air antenna is a passive antenna.

[0028] In one embodiment, an antenna array is arranged between an outer arc and an inner arc on the front cross-sectional surface of the air-to-air antenna; the inner arc is an antenna back plate of the air-to-air antenna;

[0029] The tangent slope of the arc between the first end point of the outer arc and the first inflection point is negative; the tangent slope of the arc between the first inflection point and the vertex of the outer arc is positive; and the tangent slope of the first inflection point is 0;

[0030] The arc between the second endpoint of the outer arc and the second inflection point is symmetrical about the central axis with the arc between the first endpoint of the outer arc and the first inflection point; the arc between the second inflection point and the vertex of the outer arc is symmetrical about the central axis with the arc between the first inflection point and the vertex of the outer arc; the tangent slope of the second inflection point is 0.

[0031] In a third aspect, the present application further provides a beam switching device, applied to a processing unit, comprising:

[0032] Trajectory monitoring module, used to monitor the movement trajectory of low-altitude terminals;

[0033] A time determination module, used to determine the beam switching time of the low-altitude terminal under the composite antenna according to the motion trajectory of the low-altitude terminal; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna;

[0034] A beam switching module is used to control the low-altitude terminal to perform beam switching according to the beam switching time; the beam switching means switching from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, or from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna.

[0035] In a fourth aspect, the present application further provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the following steps are implemented:

[0036] Monitor the movement trajectory of low-altitude terminals;

[0037] According to the motion trajectory of the low-altitude terminal, determining the beam switching time of the low-altitude terminal under the composite antenna; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna;

[0038] According to the beam switching time, the low-altitude terminal is controlled to perform beam switching; the beam switching means switching from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, or switching from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna.

[0039] In a fifth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the following steps are implemented:

[0040] Monitor the movement trajectory of low-altitude terminals;

[0041] According to the motion trajectory of the low-altitude terminal, determining the beam switching time of the low-altitude terminal under the composite antenna; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna;

[0042] According to the beam switching time, the low-altitude terminal is controlled to perform beam switching; the beam switching means switching from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, or switching from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna.

[0043] In a sixth aspect, the present application further provides a computer program product, including a computer program, which implements the following steps when executed by a processor:

[0044] Monitor the movement trajectory of low-altitude terminals;

[0045] According to the motion trajectory of the low-altitude terminal, determining the beam switching time of the low-altitude terminal under the composite antenna; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna;

[0046] According to the beam switching time, the low-altitude terminal is controlled to perform beam switching; the beam switching means switching from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, or switching from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna.

[0047] The above-mentioned beam switching method, device, composite antenna system, computer equipment, computer-readable storage medium and computer program product first monitor the movement trajectory of the low-altitude terminal, and then determine the beam switching time of the low-altitude terminal under the composite antenna according to the movement trajectory of the low-altitude terminal; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna; finally, according to the beam switching time, the low-altitude terminal is controlled to perform beam switching; beam switching means switching from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, or from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna. In this way, when performing beam switching, without adjusting the downtilt angle of the ground antenna, a composite antenna including a ground antenna and an air antenna is proposed, which can take into account both ground and low-altitude coverage, and an antenna backplane is set between the air antenna and the ground antenna, which can effectively isolate the air signal from the ground signal, which is beneficial to improving the signal quality, thereby reducing the interference between the air signal and the ground signal, and can make the beam switching process of the low-altitude terminal more stable, thereby achieving the purpose of seamlessly and smoothly switching the low-altitude terminal from the air beam of the air antenna to the ground beam of the ground antenna, or seamlessly and smoothly switching from the ground beam of the ground antenna to the air beam of the air antenna, thereby improving the stability of the beam switching. At the same time, by real-time monitoring the movement trajectory of the low-altitude terminal, the beam switching time of the low-altitude terminal under the composite antenna can be intelligently judged, and when the beam switching time is reached, the low-altitude terminal is controlled to perform beam switching, which is beneficial to minimize the delay in the beam switching process, ensure the continuity of the beam switching process, and no signal interruption occurs, further improving the stability of the beam switching. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the drawings required for use in the embodiments of the present application or related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0049] Figure 1 A schematic diagram of adjusting the downtilt angle of a ground base station antenna in one embodiment;

[0050] Figure 2 is a schematic flow chart of a beam switching method in an embodiment;

[0051] Figure 3 A structural block diagram of a composite antenna that takes into account both ground and low-altitude coverage in one embodiment;

[0052] Figure 4 is a structural block diagram of a composite antenna system in one embodiment;

[0053] Figure 5 is a schematic flow chart of a beam switching method in another embodiment;

[0054] Figure 6 is a structural block diagram of a beam switching device in one embodiment;

[0055] Figure 7 FIG. 4 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0057] In the joint networking scenarios of low-altitude networks and ground networks, low-altitude terminals (such as drones, low-altitude aircraft, etc.) are not only used for logistics distribution, but also for meteorological monitoring, agricultural monitoring, emergency communications, rescue operations, etc.; for these joint networking scenarios, due to conflicts and interference between ground services and low-altitude services, the signal quality of low-altitude networks and ground networks is reduced, thereby affecting data transmission rate and reliability, and seriously affecting the user experience of low-altitude networks and ground networks.

[0058] Currently, reference Figure 1The low-altitude communication network is based on the existing 5G+ communication network's coverage of ground users, taking into account low-altitude coverage, that is, adjusting the mechanical (or electronic) downtilt angle of the ground base station antenna from -6° to 0°, so as to achieve coverage of ground users while taking into account coverage of low-altitude users. This method of adjusting the mechanical (or electronic) downtilt angle of the antenna is relatively simple, and does not require the replacement of existing equipment. It only needs to adjust the physical angle of the antenna. However, the characteristics and requirements of air and ground coverage are quite different, and the isolation between them is not high enough, which will cause mutual interference between air and ground signals (beams), especially in areas with high-density user coverage; the adjustment of the antenna downtilt angle will cause cross-area coverage (i.e., inter-station interference), and the station spacing needs to be replanned and adjusted. The engineering workload is too large, and it will also cause the signal of the ground user below the antenna to weaken; the antenna cannot be fully suitable for taking into account the double-layer coverage of air and ground, which will lead to insufficient or uneven signal strength, etc. In addition, it is impossible to achieve air coverage vertically above the station, which seriously affects the communication performance of low-altitude and ground networks, as well as the user experience of low-altitude and ground networks.

[0059] Based on this, this application proposes a composite antenna design method that takes into account both ground and low-altitude coverage, effectively solving the above problems. The air coverage and ground coverage have low coupling and are independent of each other, reducing mutual interference between air and ground signals (beams), and ground coverage and capacity are not affected in any way. At the same time, it reduces the frequent switching of air beams and improves the throughput of drone services. It can significantly improve low-altitude network performance and user perception, and reduce the cost of low-altitude network and ground network construction and optimization. At the same time, based on the composite antenna, this application also proposes a beam switching method, which is conducive to improving the smoothness of beam switching.

[0060] In order to more clearly explain the beam switching method provided in the embodiment of the present application, some terms are explained as follows:

[0061] UE: User Equipment, refers to the equipment operating in the low-altitude network, such as drones. In this technical solution, UE refers to the drone that performs signal measurement and base station switching operations.

[0062] RSRP: Reference Signal Received Power, is an indicator to measure the strength of received signals in wireless networks. RSRP is used to evaluate signal quality and determine the timing of base station switching.

[0063] SINR: Signal to Interference plus Noise Ratio, is a key indicator for measuring the quality of received signals. SINR is used to evaluate the reliability of communication links and affects base station selection and handover decisions.

[0064] LOS: Line of Sight, which refers to the way signals are transmitted without any obstacles. Under LOS conditions, signal transmission loss is small and coverage is good.

[0065] HO: Handover refers to the process of switching user equipment (such as drones) from one base station to another during movement. An effective handover mechanism can improve the coverage and service continuity of low-altitude networks.

[0066] TDC(3DC): Three(3) Dimensional Coverage, which provides comprehensive wireless signal coverage in three-dimensional space for an area. Here, it refers to three-dimensional and all-round wireless signal coverage on the ground and in the air.

[0067] JK (Jig K): Usually refers to a pole assembly in antenna installation. An antenna pole is a structural support for mounting and fixing antenna equipment, usually used to install various types of antennas on the top of a building, on the ground or on other structures. An antenna pole is a vertical rod or tubular structure used to support and fix antennas. It is usually made of metal and has sufficient strength and durability to withstand the weight of the antenna and the influence of the external environment, such as wind, rain and other climatic factors.

[0068] HBA: Horizontal Beam Angle, the angle between the center line of the antenna beam and the horizontal line. It describes the direction of the antenna beam in the horizontal direction and is used to determine the directivity of the antenna in the horizontal plane to optimize signal coverage and interference management.

[0069] VBTA: Vertical Beam Tilt Angle, which refers to the angle between the center line of the antenna beam and the horizontal line in the vertical plane, usually a downward tilt angle; by adjusting the downtilt angle, the signal coverage range can be optimized and interference and signal overlap can be reduced.

[0070] HBW: Horizontal Beam Width, horizontal beam width, refers to the angular range of the antenna transmitting signals on the horizontal plane, usually measured at the point where the antenna gain drops by 3 decibels (dB). It determines the coverage of the antenna in the horizontal direction and affects the signal propagation path and the size of the coverage area.

[0071] VBW: Vertical Beam Width, vertical beam width, refers to the angular range of the antenna transmitting signals in the vertical plane, also measured at the point where the gain drops by 3 decibels (dB). It affects the distribution of the signal in the vertical direction, determines the antenna's long-range and short-range coverage capabilities and the coverage effect of different height areas.

[0072] NoB: Number of Beams, refers to the number of independent beams generated and used simultaneously in the antenna system. Increasing the number of beams can improve the directivity and capacity of the antenna, allowing more users and connections to be supported within the same spectrum, improving system efficiency and service quality.

[0073] BPA: Beam-forming Power Allocation, beam-forming power allocation, refers to the way of allocating transmit power to different beams in beamforming technology to optimize signal transmission and reception. Through reasonable power allocation, signal strength and coverage are maximized, interference is reduced, and signal quality and overall performance of the communication system are improved.

[0074] In addition, it should be noted that the low altitude involved in this application refers to a reasonable, legal and compliant low altitude range, and the low altitude terminal flies within a reasonable, legal and compliant low altitude range.

[0075] In an exemplary embodiment, Figure 2 As shown, a beam switching method is provided. This embodiment uses the method applied to a terminal (specifically, an antenna adjustment and signal processing combined unit) as an example for illustration; it can be understood that the method can also be applied to a server, and can also be applied to a system including a terminal and a server, and is implemented through the interaction between the terminal and the server. Among them, the terminal refers to a terminal including an antenna adjustment and signal processing combined unit (such as various processors), which can specifically be various personal computers, laptops, smart phones, tablet computers, etc.; the server refers to a server including an antenna adjustment and signal processing combined unit, which can specifically be implemented with an independent server or a server cluster consisting of multiple servers. In this embodiment, the method includes the following steps S201 to S203. Among them:

[0076] Step S201, monitoring the movement trajectory of the low-altitude terminal.

[0077] Among them, low-altitude terminals refer to drones, low-altitude aircraft, etc.

[0078] Among them, the motion trajectory of the low-altitude terminal may refer to the motion trajectory of a drone, a low-altitude aircraft, etc.

[0079] Exemplarily, the antenna adjustment and signal processing combined unit monitors the movement trajectory and signal strength of the low-altitude terminal in real time to intelligently determine when the low-altitude terminal performs beam switching, such as intelligently determining when the low-altitude terminal switches from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, or from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna.

[0080] It should be noted that the antenna adjustment and signal processing combined unit can be placed in the machine room or outdoors, and this application does not limit it.

[0081] Step S202, determining the beam switching time of the low-altitude terminal under the composite antenna according to the movement trajectory of the low-altitude terminal; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna.

[0082] The composite antenna includes an air-to-air antenna with all-round coverage of the air and a ground-to-ground antenna with all-round coverage of the ground; the air-to-air antenna is a circular curved three-dimensional antenna symmetrical around the central axis; the antenna back plate is used to isolate the air-to-air signal and the ground-to-ground signal to avoid interference between the air-to-air signal and the ground-to-ground signal, thereby improving the signal quality. Figure 3 The front sectional view of the composite antenna shown in the figure comprises an air-to-air antenna and three ground-to-ground antennas; AE represents the antenna backplane, JK represents the antenna pole, the structure enclosed by arcs ABCDE and arcs A'B'C'D'E' represents the air-to-air antenna, and the structures next to cells ①, ②, and ③ (such as the structure enclosed by PQ and P'Q', and the structure enclosed by MN and M'N') represent the ground-to-ground antenna.

[0083] It should be noted that the current low-altitude communication network uses the existing 5G+ ground network to achieve compatible coverage of ground and low-altitude users by adjusting the downtilt angle of the ground base station antenna, which is simple to implement; however, due to the different characteristics and requirements of air and ground coverage, signals are prone to interfere with each other, especially in high-density areas. In addition, antenna adjustment may cause cross-area coverage and signal weakening to re-plan the station spacing, which is a large amount of engineering. In addition, it is difficult to simultaneously meet the 3D (three-dimensional) stereo coverage of air and ground, and it is impossible to achieve vertical air coverage, which seriously affects the communication performance and user experience. Based on this, the present application proposes a composite antenna design method that takes into account both ground and low-altitude coverage, without changing the downtilt angle of the existing base station antenna and without affecting the ground coverage, to achieve three-dimensional seamless coverage of the ground and low altitude; effectively reduce the interference between air and ground signals (beams), solve the business conflicts between ground and low-altitude networks, reduce frequent switching, improve the business throughput of drones, improve the utilization rate of system wireless resources and low-altitude network performance, improve user experience, reduce network construction and optimization costs, and have practical value and broad application prospects.

[0084] Among them, the beam switching time refers to the beam switching timing of the low-altitude terminal under the composite antenna, specifically refers to the time when the low-altitude terminal performs beam switching under the composite antenna, such as the time when the low-altitude terminal switches from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, or the time when the low-altitude terminal switches from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna.

[0085] Exemplarily, the antenna adjustment and signal processing combined unit analyzes the motion trajectory of the low-altitude terminal to obtain a trajectory analysis result, and predicts the beam switching time of the low-altitude terminal under the composite antenna based on the trajectory analysis result; for example, the motion trajectory of the low-altitude terminal is input into a pre-trained beam switching time prediction model (such as a neural network model), and the beam switching time of the low-altitude terminal under the composite antenna is predicted by the model.

[0086] For example, when a drone gradually rises into the air or approaches the ground, the antenna adjustment and signal processing combined unit can determine when the drone switches from the ground beam of the ground antenna to the air beam of the air antenna, or when the drone switches from the air beam of the air antenna to the ground beam of the ground antenna by analyzing the motion trajectory of the drone monitored in real time.

[0087] Step S203, according to the beam switching time, control the low-altitude terminal to perform beam switching; beam switching means switching from the air beam of the air-to-air antenna to the ground beam of the ground-to-ground antenna, or from the ground beam of the ground-to-ground antenna to the air beam of the air-to-air antenna.

[0088] Among them, beam switching refers to switching from one beam to another, such as a low-altitude terminal switching from an air-to-air beam to a ground-to-ground beam, or a low-altitude terminal switching from a ground-to-air beam to an air-to-air beam.

[0089] Among them, the air beam refers to the beam radiated by the air antenna; the ground beam refers to the beam radiated by the ground antenna.

[0090] Among them, the low-altitude terminal switches from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, which means that the low-altitude terminal switches from communicating with the air-to-air beam of the air-to-air antenna to communicating with the ground-to-ground beam of the ground-to-ground antenna. Specifically, it means that during the landing process, the low-altitude terminal switches from communicating with the air-to-air beam of the air-to-air antenna to communicating with the ground-to-ground beam of the ground-to-ground antenna.

[0091] Among them, the low-altitude terminal switches from the ground beam of the ground antenna to the air beam of the air antenna, which means that the low-altitude terminal switches from communicating with the ground beam of the ground antenna to communicating with the air beam of the air antenna. Specifically, it means that during the process of the low-altitude terminal taking off from the ground, it switches from communicating with the ground beam of the ground antenna to communicating with the air beam of the air antenna.

[0092] Exemplarily, the antenna adjustment and signal processing combined unit controls the low-altitude terminal to switch from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna at the beam switching time, or controls the low-altitude terminal to switch from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna at the beam switching time.

[0093] For example, when the UAV gradually takes off from the ground, the antenna adjustment and signal processing combined unit controls the UAV to switch seamlessly and smoothly from the ground antenna (beam) to the air antenna (beam) according to the beam switching time; or, when the UAV gradually lands, the antenna adjustment and signal processing combined unit controls the UAV to switch seamlessly and smoothly from the air antenna (beam) to the ground antenna (beam) according to the beam switching time.

[0094] In the above beam switching method, the movement trajectory of the low-altitude terminal is first monitored, and then the beam switching time of the low-altitude terminal under the composite antenna is determined according to the movement trajectory of the low-altitude terminal; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna; finally, according to the beam switching time, the low-altitude terminal is controlled to perform beam switching; beam switching means switching from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, or from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna. In this way, when performing beam switching, without adjusting the downtilt angle of the ground antenna, a composite antenna including a ground antenna and an air antenna is proposed, which can take into account both ground and low-altitude coverage, and an antenna backplane is set between the air antenna and the ground antenna, which can effectively isolate the air signal from the ground signal, which is beneficial to improving the signal quality, thereby reducing the interference between the air signal and the ground signal, and can make the beam switching process of the low-altitude terminal more stable, thereby achieving the purpose of seamlessly and smoothly switching the low-altitude terminal from the air beam of the air antenna to the ground beam of the ground antenna, or seamlessly and smoothly switching from the ground beam of the ground antenna to the air beam of the air antenna, thereby improving the stability of the beam switching. At the same time, by real-time monitoring the movement trajectory of the low-altitude terminal, the beam switching time of the low-altitude terminal under the composite antenna can be intelligently judged, and when the beam switching time is reached, the low-altitude terminal is controlled to perform beam switching, which is beneficial to minimize the delay in the beam switching process, ensure the continuity of the beam switching process, and no signal interruption occurs, further improving the stability of the beam switching.

[0095] In an exemplary embodiment, the above step S202 determines the beam switching time of the low-altitude terminal under the composite antenna according to the motion trajectory of the low-altitude terminal, and specifically includes the following contents: predicting the take-off time or landing time of the low-altitude terminal according to the motion trajectory of the low-altitude terminal; using the take-off time or landing time of the low-altitude terminal as the beam switching time of the low-altitude terminal under the composite antenna.

[0096] Among them, the beam switching time of the low-altitude terminal under the composite antenna refers to the take-off time or landing time of the low-altitude terminal.

[0097] Exemplarily, the antenna adjustment and signal processing combined unit inputs the motion trajectory of the low-altitude terminal into a pre-trained beam switching time prediction model, and performs a series of analysis and processing on the motion trajectory of the low-altitude terminal through the model to obtain the take-off time or landing time of the low-altitude terminal, and uses the take-off time or landing time of the low-altitude terminal as the beam switching time of the low-altitude terminal under the composite antenna.

[0098] In this embodiment, by analyzing the motion trajectory of the low-altitude terminal, the beam switching time of the low-altitude terminal under the composite antenna can be effectively determined, so that when the beam switching time is reached, the low-altitude terminal can be controlled to perform beam switching, which is beneficial to minimize the delay in the beam switching process, ensure the continuity of the beam switching process, and prevent signal interruption, thereby further improving the smoothness of the beam switching.

[0099] In an exemplary embodiment, the above step S203 controls the low-altitude terminal to perform beam switching according to the beam switching time, and specifically includes the following contents: when it is identified according to the motion trajectory that the low-altitude terminal is in a state to be ready for takeoff, the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna are jointly adjusted according to the beam switching time, so that the low-altitude terminal switches from the ground-to-ground beam of the ground-to-air antenna to the air-to-air beam of the ground-to-air antenna; when it is identified according to the motion trajectory that the low-altitude terminal is in a state to be ready for landing, the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna are jointly adjusted according to the beam switching time, so that the low-altitude terminal switches from the air-to-air beam of the air-to-ground antenna to the ground beam of the ground-to-ground antenna.

[0100] Among them, the low-altitude terminal is in a state ready for takeoff, which means that the low-altitude terminal is ready to take off.

[0101] Among them, the low-altitude terminal is in a state of waiting to land, which means that the low-altitude terminal is preparing to land.

[0102] Among them, the antenna array of the ground antenna and the antenna array of the air antenna are precisely jointly controlled to reconstruct and adjust the direction of the ground beam or the air beam to seamlessly switch to the air beam or the ground beam. The entire beam switching process is imperceptible to the low-altitude terminal.

[0103] Exemplarily, when it is identified based on the motion trajectory that the low-altitude terminal is in a state of waiting to take off, the antenna adjustment and signal processing combined unit determines whether the current time has reached the beam switching time. When the beam switching time is reached, the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna are jointly adjusted to achieve rapid beam reconstruction and direction adjustment, so that the low-altitude terminal switches from the ground beam of the ground-to-air antenna to the air beam of the air-to-air antenna. When it is identified based on the motion trajectory that the low-altitude terminal is in a state of waiting to land, the antenna adjustment and signal processing combined unit determines whether the current time has reached the beam switching time. When the beam switching time is reached, the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna are jointly adjusted to achieve rapid beam reconstruction and direction adjustment, so that the low-altitude terminal switches from the air beam of the air-to-air antenna to the ground beam of the ground antenna.

[0104] For example, during the take-off phase of a drone, the ground-to-air antenna array will be responsible for communicating with the drone and will gradually adjust the beam direction as the drone takes off; when the drone reaches a certain height, the communication system begins to prepare to switch the air-to-ground antenna array. At this time, the beam directions of the ground-to-ground antenna and the air-to-ground antenna will overlap briefly to ensure signal continuity; after the switch is completed, the air-to-ground antenna array begins to communicate with the drone, and the drone enters a stable flight phase.

[0105] In this embodiment, the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna are jointly adjusted according to the beam switching time, so that rapid beam reconstruction and direction adjustment can be achieved, so that communication will not be interrupted during the beam switching process, thereby ensuring the continuity of the beam switching process and further improving the smoothness of the beam switching.

[0106] In an exemplary embodiment, the beam switching method provided in the present application also includes the step of adjusting the beam direction and beam power of the air beam, which specifically includes the following contents: when the low-altitude terminal switches from the ground beam of the ground antenna to the air beam of the air antenna, obtaining a first signal strength difference between the air beam and the ground beam; according to the first signal strength difference, adjusting the beam direction and beam power of the air beam so that the signal strength of the adjusted air beam reaches the signal strength of the ground beam.

[0107] The first signal strength difference indicates the attenuated signal strength of the air beam compared to the ground beam.

[0108] Exemplarily, when the low-altitude terminal switches from the ground beam of the ground antenna to the air beam of the air antenna, the antenna adjustment and signal processing combined unit calculates the first signal strength difference between the air beam and the ground beam based on the real-time measured signal strength of the air beam and the signal strength of the ground beam, and adjusts the beam direction and beam power of the air beam based on the first signal strength difference so that the adjusted signal strength of the air beam reaches the signal strength of the ground beam.

[0109] In this embodiment, when the low-altitude terminal switches from the ground beam of the ground antenna to the air beam of the air antenna, the first signal strength difference between the air beam and the ground beam is used to adjust the beam direction and beam power of the air beam to compensate for possible signal strength attenuation, thereby ensuring the signal quality of the beam after switching, facilitating a seamless and smooth beam switching process and further improving the smoothness of the beam switching.

[0110] In an exemplary embodiment, the beam switching method provided in the present application also includes the step of adjusting the beam direction and beam power of the ground beam, which specifically includes the following contents: when the low-altitude terminal switches from the air-to-air beam of the air-to-air antenna to the ground beam of the ground antenna, obtaining a second signal strength difference between the ground beam and the air beam; according to the second signal strength difference, adjusting the beam direction and beam power of the ground beam so that the signal strength of the adjusted ground beam reaches the signal strength of the air beam.

[0111] The second signal strength difference indicates the attenuated signal strength of the ground beam compared to the air beam.

[0112] Exemplarily, when a low-altitude terminal switches from the air-to-air beam of an air-to-air antenna to the ground-to-ground beam of a ground-to-ground antenna, the antenna adjustment and signal processing combined unit calculates the second signal strength difference between the ground beam and the air beam based on the real-time measured signal strength of the ground beam and the signal strength of the air beam, and adjusts the beam direction and beam power of the ground beam based on the second signal strength difference so that the adjusted signal strength of the ground beam reaches the signal strength of the air beam.

[0113] In this embodiment, when the low-altitude terminal switches from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, the second signal strength difference between the ground-to-air beam and the air-to-air beam is used to adjust the beam direction and beam power of the ground beam to compensate for possible signal strength attenuation, thereby ensuring the signal quality of the beam after switching, facilitating a seamless and smooth beam switching process and further improving the smoothness of the beam switching.

[0114] In an exemplary embodiment, Figure 4As shown, a composite antenna system is provided, including: a composite antenna and a processing unit (i.e., an antenna adjustment and signal processing combined unit), wherein: the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna; the processing unit is used to execute a beam switching method.

[0115] The processing unit is a combined antenna adjustment and signal processing unit, which is used to perform the following operations: Figure 2 It should be noted that when the antenna adjustment and signal processing unit performs the beam switching method, reference can be made to step S201 to step S203, which will not be described in detail here.

[0116] The composite antenna system, when performing beam switching, proposes a composite antenna including a ground antenna and an air antenna without adjusting the downtilt angle of the ground antenna, which can take into account both ground and low-altitude coverage, and an antenna backplane is set between the air antenna and the ground antenna, which can effectively isolate the air signal from the ground signal, which is beneficial to improving the signal quality, thereby reducing the interference between the air signal and the ground signal, and can make the beam switching process of the low-altitude terminal more stable, thereby achieving the purpose of seamlessly and smoothly switching the low-altitude terminal from the air beam of the air antenna to the ground beam of the ground antenna, or seamlessly and smoothly switching from the ground beam of the ground antenna to the air beam of the air antenna, thereby improving the stability of the beam switching. At the same time, by real-time monitoring the movement trajectory of the low-altitude terminal, the beam switching time of the low-altitude terminal under the composite antenna can be intelligently judged, and when the beam switching time is reached, the low-altitude terminal is controlled to perform beam switching, which is beneficial to minimize the delay in the beam switching process, ensure the continuity of the beam switching process, and prevent signal interruption, further improving the stability of the beam switching.

[0117] In an exemplary embodiment, referring to Figure 3 The air-to-air antenna (i.e., the structure enclosed by the arcs ABCDE and A'B'C'D'E') is a circular curved three-dimensional antenna symmetrical around the central axis; the air-to-air antenna is arranged above the antenna back plate (AE) and is fixed to the antenna pole (JK) through the antenna back plate; the ground-to-ground antenna is arranged below the antenna back plate (AE) and is fixed to the antenna pole (JK) through a support (such as a screw).

[0118] The overall shape of the air-to-air antenna is a circular curved solid, and its front cross-section is as follows: Figure 3 As shown, the front cross-sectional surface is rotated 180° around the central axis to form a curved three-dimensional antenna; the front cross-sectional surface is left-right symmetrical about the central axis.

[0119] The supporting member mainly plays a supporting role, specifically, is used to fix the ground-to-ground antenna on the antenna pole.

[0120] In this embodiment, the air-to-ground antenna is a circular curved three-dimensional antenna symmetrical around the central axis, which can achieve all-round air coverage and solve the problem of dark lights. At the same time, an antenna backplane is arranged between the air-to-ground antenna and the ground-to-ground antenna, which is conducive to effectively isolating the air-to-ground signal from the ground signal and avoiding mutual interference between the air-to-ground signal and the ground signal.

[0121] In an exemplary embodiment, referring to Figure 3 The number of air-to-air antennas is 1, and the air-to-air antenna corresponds to one cell (such as cell ④), which is used to achieve full air coverage; the number of ground-to-ground antennas is 3, each ground-to-ground antenna corresponds to one cell (such as cell ①, cell ②, cell ③), and the angle between each ground-to-ground antenna is 120 degrees, which is used to achieve full ground coverage.

[0122] There are three ground-to-ground antennas, and the angle between each ground-to-ground antenna is 120 degrees, in order to achieve 360° all-round coverage of the ground.

[0123] In this embodiment, the ground antenna and the air antenna together form a composite antenna, achieving 3D stereo coverage of 4 cells on one pole, taking into account both sky and ground coverage, reducing mutual interference between air signals and ground signals, resolving service conflicts between ground networks and low-altitude networks, and saving network construction and optimization costs.

[0124] In an exemplary embodiment, referring to Figure 3 , the ground-to-air antenna and the air-to-air antenna are of the same frequency and the same standard; or, the ground-to-air antenna and the air-to-air antenna are of the same frequency and different standards; or, the ground-to-air antenna and the air-to-air antenna are of different frequencies and the same standard; or, the ground-to-air antenna and the air-to-air antenna are of different frequencies and different standards.

[0125] Among them, the same frequency means that the ground antenna and the air antenna operate at the same frequency; the different frequencies means that the ground antenna and the air antenna operate at different frequencies.

[0126] Among them, the same standard means that the ground antenna and the air antenna follow the same communication protocol or standard; different standards mean that the ground antenna and the air antenna follow different communication protocols or standards.

[0127] In this embodiment, the ground-to-air antenna and the air-to-ground antenna in the composite antenna can be of the same frequency and the same standard, the same frequency and different standards, or different frequencies and the same standard, or different frequencies and different standards. It has flexible configuration, a wide range of applications, and strong scene adaptability.

[0128] In an exemplary embodiment, referring to Figure 3 , both the ground-to-air antenna and the air-to-air antenna are passive antennas; or, both the ground-to-air antenna and the air-to-air antenna are active antennas; or, the ground-to-air antenna is a passive antenna and the air-to-air antenna is an active antenna; or, the ground-to-air antenna is an active antenna and the air-to-air antenna is a passive antenna.

[0129] Among them, there are many combinations of ground-to-ground antennas and air-to-air antennas in the composite antenna, such as passive + passive, active + active, passive + active, and active + passive.

[0130] In this embodiment, the composite antenna is suitable for both passive antennas for the ground and air or both active antennas, and is also suitable for various forms such as passive and active hybrid antennas. It has flexible combinations, strong adaptability, and a wide range of applications.

[0131] In an exemplary embodiment, referring to Figure 3 An antenna array is arranged between the outer arc (ABCDE arc) and the inner arc (A'B'C'D'E' arc) on the positive analysis surface of the air-to-air antenna; the inner arc (A'B'C'D'E' arc) is the antenna back plate of the air-to-air antenna; the tangent slope of the arc (AB arc) between the first end point (A) of the outer arc and the first inflection point (B) is negative; the tangent slope of the arc (BC arc) between the first inflection point (B) and the vertex (C) of the outer arc is positive; the tangent slope of the first inflection point (B) is 0; the arc (ED arc) between the second end point (E) of the arc and the second inflection point (D) is symmetrical with the arc (AB arc) between the first end point (A) of the outer arc and the first inflection point (B) about the central axis; the arc (DC arc) between the second inflection point (D) and the vertex (C) of the outer arc is symmetrical with the arc (BC arc) between the first inflection point (B) and the vertex (C) of the outer arc about the central axis; the tangent slope of the second inflection point (D) is 0.

[0132] Among them, the A'B'C'D'E' arc corresponds to the inner side of the ABCDE arc. The A'B'C'D'E' arc is the antenna backplane, which plays an isolation role and reduces the mutual interference between the air and ground signals (beams). The space between the two arcs is filled with (passive or active) large-scale antenna arrays to meet the air coverage gain requirements.

[0133] In this embodiment, an inflection point is set, and the tangent slope of the inflection point is 0, the tangent slopes of the arcs before and after the inflection point are negative and positive, and are symmetrical about the central axis, which is conducive to achieving seamless and smooth switching between the ground antenna (beam) and the air antenna (beam), thereby improving the smoothness of the beam switching.

[0134] In an exemplary embodiment, Figure 5 As shown, another beam switching method is provided, which is described by taking the application of the method to a terminal (specifically, an antenna adjustment and signal processing combined unit) as an example, including the following steps S501 to S509.

[0135] in:

[0136] Step S501, monitoring the movement trajectory of the low-altitude terminal.

[0137] Step S502, predicting the take-off time or landing time of the low-altitude terminal according to the motion trajectory of the low-altitude terminal.

[0138] Step S503, taking the take-off time or landing time of the low-altitude terminal as the beam switching time of the low-altitude terminal under the composite antenna; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna.

[0139] Among them, after step S503, there are two step branches, namely step S504 to step S506 and step S507 to step S509.

[0140] Step S504, when it is identified based on the motion trajectory that the low-altitude terminal is in a state of waiting to take off, the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna are jointly adjusted according to the beam switching time, so that the low-altitude terminal switches from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna.

[0141] Step S505: When the low-altitude terminal switches from the ground beam of the ground-to-ground antenna to the air beam of the air-to-air antenna, a first signal strength difference between the air beam and the ground beam is obtained.

[0142] Step S506: adjusting the beam direction and beam power of the air beam according to the first signal strength difference, so that the signal strength of the air beam after adjustment reaches the signal strength of the ground beam.

[0143] Step S507, when it is identified based on the motion trajectory that the low-altitude terminal is in a state of waiting to land, the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna are jointly adjusted according to the beam switching time, so that the low-altitude terminal switches from the air-to-air beam of the air-to-air antenna to the ground beam of the ground antenna.

[0144] Step S508: When the low-altitude terminal switches from the air beam of the air-to-air antenna to the ground beam of the ground-to-ground antenna, a second signal strength difference between the ground beam and the air beam is obtained.

[0145] Step S509: adjusting the beam direction and beam power of the ground beam according to the second signal strength difference, so that the signal strength of the adjusted ground beam reaches the signal strength of the air beam.

[0146] In the above beam switching method, when performing beam switching, without adjusting the downtilt angle of the ground antenna, a composite antenna including a ground antenna and an air antenna is proposed, which can take into account both ground and low-altitude coverage, and an antenna backplane is set between the air antenna and the ground antenna, which can effectively isolate the air signal from the ground signal, which is beneficial to improving the signal quality, thereby reducing the interference between the air signal and the ground signal, and can make the beam switching process of the low-altitude terminal more stable, thereby achieving the purpose of seamlessly and smoothly switching the low-altitude terminal from the air beam of the air antenna to the ground beam of the ground antenna, or seamlessly and smoothly switching from the ground beam of the ground antenna to the air beam of the air antenna, thereby improving the stability of the beam switching. At the same time, by real-time monitoring the motion trajectory of the low-altitude terminal, the beam switching time of the low-altitude terminal under the composite antenna can be intelligently judged, and when the beam switching time is reached, the low-altitude terminal is controlled to perform beam switching, which is beneficial to minimize the delay in the beam switching process, ensure the continuity of the beam switching process, and no signal interruption will occur, further improving the stability of the beam switching.

[0147] In order to more clearly illustrate the composite antenna system provided by the embodiment of the present application, the composite antenna system is specifically described below using a specific embodiment. In an exemplary embodiment, Figure 3 and Figure 4 As shown, the present application also provides a composite antenna design method that takes into account both ground and low-altitude coverage. By utilizing the characteristic that the downtilt angle of the existing base station antenna remains unchanged, that is, without affecting the existing ground coverage, a novel composite antenna is designed to achieve three-dimensional seamless coverage of the air area and the ground area. The new antenna is a curved surface design that is symmetrical around the central axis. It can achieve smooth signal switching during the take-off and landing of the drone, ensure the business continuity of the low-altitude drone, and achieve 360° all-round coverage of the drone at low altitude. Through the composite antenna structure, and through the combination of antenna adjustment and signal processing, the mutual interference between the air and ground signals (beams) is reduced, which not only solves the business conflict between the ground network and the low-altitude network, reduces frequent switching, and improves the drone service throughput, but also improves the system wireless resource utilization, improves the low-altitude network performance and user experience, reduces the network construction and optimization costs, and has good practical value and broad application prospects.

[0148] The mechanical (or electronic) downtilt angle of the antenna on the ground base station is not adjusted, and the downtilt angle (for example, -6°) remains unchanged, so as not to affect the existing ground coverage. A novel low-altitude coverage antenna is designed and placed on the original ground coverage 3-cell antenna. This novel antenna design scheme is as follows Figure 3 As shown, where:

[0149] 1) The novel antenna is a circular curved solid, and its front cross-section is as follows Figure 3 As shown, the front cross-sectional surface is rotated 180° around the central axis to form a curved three-dimensional antenna; the front cross-sectional surface is left-right symmetrical about the central axis.

[0150] 2) AE is the antenna backplane, which plays a supporting and isolating role. Support means that this special antenna can be fixed on the top of the antenna pole (JK) or on the top of the antenna pole (JK). Isolation means isolating the signal (beam) radiated by the low-altitude antenna from affecting ground users (the low-altitude antenna above does not affect the ground coverage of the 3-cell antenna below), and isolating the signal (beam) radiated by the ground antenna from affecting low-altitude users (the 3-cell antenna below does not affect the air coverage of the low-altitude antenna above).

[0151] 3) The tangent slope of the AB arc is negative, and its average tangent slope is approximately the downtilt angle of the ground antenna, which provides partial ground coverage while taking into account excessive coverage of the mid-air. When the UAV takes off from the ground (or lands), the ground antenna (beam) and the air antenna (beam) are seamlessly and smoothly switched, which improves the smoothness of the switching and ensures the continuity of the low-altitude UAV business. The ED arc is symmetrical with the AB arc about the central axis.

[0152] 4) Point B is the inflection point, and the tangent slope is 0, realizing the transition between ground and air coverage.

[0153] 5) The tangent slope of the BC arc is positive, achieving air coverage; the DC arc and the BC arc are symmetrical about the central axis.

[0154] 6) Arc A'B'C'D'E' corresponds to the inner side of arc ABCDE. Arc A'B'C'D'E' is the antenna backplane, which plays an isolation role and reduces the mutual interference between air and ground signals (beams). The space between the two arcs is filled with large-scale antenna arrays (passive or active) to meet the air coverage gain requirements.

[0155] 7) Achieve 360° all-round coverage of low-altitude drones without blind spots, solving the problem of dark lights above the lights, that is, it not only solves the surrounding air coverage, but also solves the air coverage vertically above the base station.

[0156] 8) 360° all-round coverage without blind spots in the air reduces the frequent switching of drones in the air (especially when hovering), improves the throughput of drone services, improves low-altitude network performance and user experience, and improves the utilization rate of system wireless resources.

[0157] 9) The ground-facing antenna and the air-facing antenna together form a composite antenna, achieving 3D coverage of 4 cells on one pole, taking into account both sky and ground coverage, reducing mutual interference between them, resolving service conflicts between ground networks and low-altitude networks, and saving network construction and optimization costs.

[0158] refer to Figure 4, the present application also proposes a composite antenna system that takes into account both ground and low-altitude coverage; wherein:

[0159] 1) The ground antennas in the composite antenna correspond to cells 1, 2 and 3, maintaining ground coverage (serving ground terminals such as mobile phones, tablets, computers, CPE, etc.), such as Figure 4 As shown in the lower middle part, the conical part below the antenna backplane is the ground (coverage) beam set; its beam parameters include: number of beams NoB (N for each cell), horizontal beam angle HBA (0~120°), vertical beam downtilt angle VBTA (0~-90°), horizontal beam width HBW, vertical beam width VBW, beam allocation power BPA, etc., which meet the originally planned ground coverage and capacity requirements.

[0160] 2) The air-to-air antenna in the composite antenna corresponds to cell 4, achieving all-round air coverage without blind spots (serving low-altitude terminals, such as drones, aircraft, etc.), such as Figure 4 As shown in the upper middle part, the conical part above the antenna backplane is the air (coverage) beam set; its beam parameters include: the number of beams NoB (the cell is 3N, that is, the number of air special cell beams is three times the number of ground cell beams), beam horizontal direction angle HBA (0~360°), beam vertical downtilt angle VBTA (or elevation angle) (0~+90°), horizontal beam width HBW, vertical beam width VBW, beam allocation power BPA, etc.; ensure that aerial terminals at any angle within the coverage range can receive signals, and flexibly adjust the beam width and power according to the mobility characteristics and needs of the aerial terminals to optimize the low-altitude coverage effect.

[0161] 3) The ground antenna (cells 1, 2 and 3) and the air antenna (cell 4) in the composite antenna can be of the same frequency and the same standard, the same frequency and different standards, or different frequencies and the same standard, or different frequencies and different standards. It has flexible configuration, a wide range of applications and strong scene adaptability.

[0162] 4) Figure 4 As shown by the beam switching arrow, when the drone takes off from the ground (or lands), it can achieve seamless and smooth switching from the ground antenna (beam) to the air antenna (beam), or from the air antenna (beam) to the ground antenna (beam). Here, antenna adjustment and signal processing need to be closely combined. The smoothness of this process is ensured by adding an antenna adjustment and signal processing combination unit. The specific functions and processing process of the antenna adjustment and signal processing combination unit are as follows:

[0163] 4.1) Using advanced signal processing algorithms - antenna (beam) switching algorithms, the drone's trajectory and signal strength are monitored in real time. When the drone gradually rises or approaches the ground, the system can intelligently determine when to switch between the ground antenna (beam) and the air antenna (beam);

[0164] 4.2) Through precise joint control of the ground and air antenna arrays, rapid beam reconstruction and direction adjustment are achieved, so that the switching process between the ground antenna (beam) and the air antenna (beam) will not interrupt communication;

[0165] 4.3) Signal attenuation compensation: During the switching process between the ground antenna (beam) and the air antenna (beam), the system will dynamically adjust the beam direction and beam power according to the real-time measured signal strength to compensate for possible signal attenuation and ensure signal quality;

[0166] 4.4) Switching delay optimization: By optimizing the signal processing path and the switching algorithm between the ground antenna (beam) and the air antenna (beam), the delay during the switching process is minimized to ensure the continuity of drone control and data transmission.

[0167] This composite antenna system achieves efficient and seamless coverage of the ground and air through ingenious antenna design and the combination of antenna adjustment and signal processing technology, providing strong support for future 6G communication systems.

[0168] It should be noted that 1) the composite antenna in the technical solution of the present application is suitable for both passive antennas for the ground and the air or both active antennas, and is suitable for various forms (formats) such as passive and active hybrid antennas, that is, passive + passive, active + active, passive + active or active + passive for the ground + air, with flexible combinations, strong adaptability and a wide range of applications. 2) Since low-altitude coverage is usually line-of-sight propagation (LOS) and the loss to the air is relatively small, the distance between low-altitude base stations is usually 3 to 5 times that of ground base stations, saving the number of base station deployments and transmission power (power consumption). 3) The switching conditions of the technical solution of the present application can be based on the broadcast beam (or service beam) RSRP, the broadcast beam (or service beam) SINR, or the broadcast beam (or service beam) RSRP+SINR.

[0169] It should be noted that the composite antenna proposed in this application has the following technical points:

[0170] 1) A composite antenna design method that takes into account both ground and low-altitude coverage is introduced.

[0171] 2) A method for adding a low-altitude coverage antenna without affecting the ground coverage range and capacity while keeping the downtilt angle of the ground base station antenna unchanged.

[0172] 3) A novel circular curved solid antenna design method is used, which is symmetrical about the front analysis surface and forms a curved solid antenna.

[0173] 4) The antenna backplane is used for support and isolation to ensure that low-altitude and ground antennas do not interfere with each other.

[0174] 5) A novel composite antenna design and combination to achieve seamless switching between ground and low altitude and improve switching smoothness.

[0175] 6) Specially designed inflection points enable transition from ground to low-altitude coverage.

[0176] 7) The low-altitude coverage antenna design achieves 360° coverage without blind spots in the air, improves air coverage performance, and solves the "darkness above the lights" problem.

[0177] 8) An isolation structure is designed inside the antenna to reduce mutual interference between air and ground signals.

[0178] 9) Composite antennas achieve three-dimensional coverage, taking into account both the sky and the ground, and reducing the structure and method of mutual interference.

[0179] 10) The antenna design allows flexible configuration, supports the combination of same-frequency and different-frequency, same-standard and different-standard, and supports different forms of passive and active.

[0180] 11) Add antenna adjustment and signal processing combined unit to ensure smooth signal switching.

[0181] 12) Use signal processing algorithms to intelligently determine the timing of antenna switching.

[0182] 13) Accurately jointly control the antenna array to achieve rapid beam reconstruction and direction adjustment, dynamically adjust the beam direction and power, compensate for signal attenuation, and ensure signal quality.

[0183] 14) Optimize the switching algorithm, reduce switching delay, and ensure communication continuity.

[0184] 15) Methods and processes to effectively eliminate service conflicts between ground networks and low-altitude networks, reduce interference, and improve the overall performance of 5G+ / 6G networks.

[0185] 16) Improve the network switching mechanism, beam and resource adjustment and management mechanism, and improve the methods and processes for drone users to experience low-altitude networks.

[0186] The composite antenna and composite antenna system proposed in this application can achieve the following technical effects:

[0187] (1) This application proposes a composite antenna design method that takes into account both ground and low-altitude coverage, which achieves three-dimensional seamless coverage of the ground and low altitude without changing the downtilt angle of the existing base station antenna and without affecting the ground coverage. It effectively reduces the interference between air and ground signals (beams), solves the service conflicts between ground and low-altitude networks, reduces frequent switching, improves the service throughput of drones, improves the utilization rate of system wireless resources and low-altitude network performance, improves user experience, reduces network construction and optimization costs, and has practical value and broad application prospects.

[0188] (2) Compared with the existing technology, the main advantages are: 1. Through the design of the composite antenna, without changing the ground coverage of the existing base station antenna, three-dimensional seamless coverage of the ground and air is achieved, the throughput of low-altitude UAV services is improved, and the utilization rate of system resources is improved; 2. The antenna backplane design effectively isolates the air and ground signals, improves the signal quality, effectively reduces the interference between the air and ground signals (beams), and solves the conflict between the ground and low-altitude network services; 3. It supports multiple combinations of air and ground networks with the same frequency, different frequencies and different standards, and also supports multiple combinations of passive antennas and active antennas with different antenna forms, which is suitable for various scenarios, has strong adaptability and a wide range of applications; 4. It optimizes the antenna (or beam) switching during the take-off and landing of the UAV, and reduces the frequent switching of the UAV when flying in the air, thereby improving the network performance and user experience; 5. It is optimized on the existing 5G+ network, has strong compatibility, low transformation workload, saves the network construction and optimization costs of the low-altitude network, and has high practical value.

[0189] (3) 1. In the scenario of 5G+ / 6G low-altitude network and ground network joint networking, a novel antenna structure and design method are innovatively proposed, using a rotationally symmetrical curved antenna design and combining antenna adjustment with signal processing to meet the complex three-dimensional coverage requirements of air and ground, making the management and allocation of network resources more flexible and improving overall network performance; 2. An innovative isolation structure is proposed, using the antenna backplane to isolate air and ground signals (beams), providing an innovative solution to reduce interference between signals (beams); 3. The composite antenna achieves 360° dead zone 1. It realizes all-round stereo coverage of the UAV, solves the problem of "darkness above the light" of traditional antennas, and improves network reliability and UAV service continuity; 2. It realizes multiple uses of one pole (4-cell 3D stereo coverage), which solves the service conflict between ground and low-altitude networks; 3. It supports multiple frequency and standard combinations as well as passive, active and hybrid form combinations, providing greater flexibility and applicability; 4. It optimizes the antenna (or beam) switching during the take-off and landing of the UAV, and reduces the frequent switching of the UAV when flying in the air, ensuring the smooth transition of the signal and service continuity, and improving the network performance and user experience.

[0190] (4) It can bring certain practical value: 1. By effectively solving the conflicts and interferences between low-altitude networks and ground networks, the reliability and stability of the entire network can be improved, and the satisfaction of ground and low-altitude users can be improved; 2. The efficiency of the entire communication system can be improved, and the communication quality between drones and low-altitude networks can be improved; 3. Through the design of composite antennas, three-dimensional seamless coverage of the ground and air can be achieved, network performance and system resource utilization can be improved, and operators can be provided with significant market competitive advantages; 4. The combination of creative antenna adjustment and signal processing can provide enterprises with a leading position in technology, maximize the value of existing infrastructure, and reduce the cost of low-altitude networks and ground networks. 5. Provide reliable network support for application scenarios such as intelligent transportation, smart logistics, and agricultural monitoring, adapt to different flight conditions, and expand the application potential of UAV technology in different fields and scenarios; 6. The deployment and implementation of this system will promote technological innovation, promote technological progress and industrial development of low-altitude networks, and promote the popularization of UAV applications; 7. Through scientific layout and dynamic adjustment, the overall performance and benefits of the communication system are improved, and it is committed to improving the reliability and flexibility of the future mobile communication system 6G, which provides support for the development of future network 6G and has high promotion and application value.

[0191] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0192] Based on the same inventive concept, the embodiment of the present application also provides a beam switching device for implementing the beam switching method involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in one or more beam switching device embodiments provided below can refer to the limitations on the beam switching method above, and will not be repeated here.

[0193] In an exemplary embodiment, Figure 6 As shown, a beam switching device is provided, including: a trajectory monitoring module 610, a time determination module 620 and a beam switching module 630, wherein:

[0194] The trajectory monitoring module 610 is used to monitor the movement trajectory of the low-altitude terminal.

[0195] The time determination module 620 is used to determine the beam switching time of the low-altitude terminal under the composite antenna according to the movement trajectory of the low-altitude terminal; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna.

[0196] The beam switching module 630 is used to control the low-altitude terminal to perform beam switching according to the beam switching time; beam switching means switching from the air beam of the air-to-air antenna to the ground beam of the ground-to-ground antenna, or from the ground beam of the ground-to-ground antenna to the air beam of the air-to-air antenna.

[0197] In an exemplary embodiment, the time determination module 620 is also used to predict the take-off time or landing time of the low-altitude terminal according to the motion trajectory of the low-altitude terminal; and use the take-off time or landing time of the low-altitude terminal as the beam switching time of the low-altitude terminal under the composite antenna.

[0198] In an exemplary embodiment, the beam switching module 630 is also used to, when it is identified according to the motion trajectory that the low-altitude terminal is in a state ready to take off, jointly adjust the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna according to the beam switching time, so that the low-altitude terminal switches from the ground-to-ground beam of the ground-to-air antenna to the air-to-air beam of the ground-to-air antenna; when it is identified according to the motion trajectory that the low-altitude terminal is in a state ready to land, jointly adjust the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna according to the beam switching time, so that the low-altitude terminal switches from the air-to-air beam of the air-to-ground antenna to the ground-to-ground beam of the ground-to-ground antenna.

[0199] In an exemplary embodiment, the beam switching device also includes a first adjustment module, which is used to obtain a first signal strength difference between the air beam and the ground beam when the low-altitude terminal switches from the ground beam of the ground antenna to the air beam of the air antenna; according to the first signal strength difference, adjust the beam direction and beam power of the air beam so that the signal strength of the adjusted air beam reaches the signal strength of the ground beam.

[0200] In an exemplary embodiment, the beam switching device also includes a second adjustment module, which is used to obtain a second signal strength difference between the ground beam and the air beam when the low-altitude terminal switches from the air beam of the air antenna to the ground beam of the ground antenna; according to the second signal strength difference, adjust the beam direction and beam power of the ground beam so that the signal strength of the adjusted ground beam reaches the signal strength of the air beam.

[0201] Each module in the above-mentioned beam switching device can be implemented in whole or in part by software, hardware and a combination thereof. Each of the above-mentioned modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute the operations corresponding to each of the above modules.

[0202] In an exemplary embodiment, a computer device is provided. The computer device may be a terminal, and its internal structure diagram may be as shown in FIG. Figure 7 As shown. The computer device includes a processor, a memory, an input / output interface, a communication interface, a display unit and an input device. The processor, the memory and the input / output interface are connected via a system bus, and the communication interface, the display unit and the input device are connected to the system bus via the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be implemented through WIFI, a mobile cellular network, near field communication (NFC) or other technologies. When the computer program is executed by the processor, a beam switching method is implemented. The display unit of the computer device is used to form a visually visible picture, which can be a display screen, a projection device or a virtual reality imaging device. The display screen can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covering the display screen, or a button, trackball or touchpad set on the computer device shell, or an external keyboard, touchpad or mouse.

[0203] Those skilled in the art will understand that Figure 7 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0204] In one embodiment, a computer device is further provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above method embodiments when executing the computer program.

[0205] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0206] In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0207] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0208] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, an artificial intelligence (AI) processor, etc., but are not limited to this.

[0209] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0210] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A beam switching method, characterized in that: Applied to a processing unit, the method comprises: Monitor the movement trajectory of low-altitude terminals; According to the motion trajectory of the low-altitude terminal, determining the beam switching time of the low-altitude terminal under the composite antenna; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna; According to the beam switching time, the low-altitude terminal is controlled to perform beam switching; the beam switching means switching from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, or switching from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna.

2. The method according to claim 1, characterized in that The step of determining the beam switching time of the low-altitude terminal under the composite antenna according to the motion trajectory of the low-altitude terminal includes: Predicting the take-off time or landing time of the low-altitude terminal according to the motion trajectory of the low-altitude terminal; The take-off time or landing time of the low-altitude terminal is used as the beam switching time of the low-altitude terminal under the composite antenna.

3. The method according to claim 1, characterized in that The controlling the low-altitude terminal to perform beam switching according to the beam switching time includes: When it is identified according to the motion trajectory that the low-altitude terminal is in a state of waiting to take off, the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna are jointly adjusted according to the beam switching time, so that the low-altitude terminal switches from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna; When it is identified according to the motion trajectory that the low-altitude terminal is in a state of waiting to land, the antenna array of the air-to-air antenna and the antenna array of the ground-to-ground antenna are jointly adjusted according to the beam switching time, so that the low-altitude terminal switches from the air-to-air beam of the air-to-air antenna to the ground beam of the ground-to-ground antenna.

4. The method according to claim 3, characterized in that The method further comprises: When the low-altitude terminal switches from the ground beam of the ground-to-ground antenna to the air beam of the air-to-air antenna, obtaining a first signal strength difference between the air beam and the ground beam; According to the first signal strength difference, the beam direction and beam power of the air beam are adjusted so that the signal strength of the adjusted air beam reaches the signal strength of the ground beam.

5. The method according to claim 3, characterized in that: The method further comprises: When the low-altitude terminal switches from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, obtaining a second signal strength difference between the ground-to-ground beam and the air-to-air beam; According to the second signal strength difference, the beam direction and beam power of the ground beam are adjusted so that the signal strength of the adjusted ground beam reaches the signal strength of the air beam.

6. A composite antenna system, characterized in that: The system comprises: a composite antenna and a processing unit; The composite antenna comprises an air-to-air antenna and a ground-to-ground antenna, and an antenna back plate is arranged between the air-to-air antenna and the ground-to-ground antenna; The processing unit is used to execute the method according to any one of claims 1 to 5.

7. The system according to claim 6, characterized in that The air-to-air antenna is a circular curved three-dimensional antenna symmetrical around the central axis; the air-to-air antenna is arranged above the antenna back plate and is fixed to the antenna pole through the antenna back plate; The ground-to-ground antenna is arranged below the antenna back plate and is fixed on the antenna pole through a support member.

8. The system according to claim 6, characterized in that The number of the air-to-air antennas is 1, and the air-to-air antenna corresponds to one cell, so as to achieve all-round air coverage; The number of the ground antennas is 3, each ground antenna corresponds to a cell, and the angle between each ground antenna is 120 degrees, so as to achieve all-round ground coverage.

9. The system according to claim 6, characterized in that The ground-to-air antenna and the air-to-air antenna are of the same frequency and the same standard; or, the ground-to-air antenna and the air-to-air antenna are of the same frequency and different standards; or, the ground-to-air antenna and the air-to-air antenna are of different frequencies and the same standard; Alternatively, the ground-to-ground antenna and the air-to-air antenna are of different frequencies and standards.

10. The system according to claim 6, characterized in that The ground-to-air antenna and the air-to-air antenna are both passive antennas; or, the ground-to-air antenna and the air-to-air antenna are both active antennas; or, the ground-to-air antenna is a passive antenna and the air-to-air antenna is an active antenna; or, the ground-to-air antenna is an active antenna and the air-to-air antenna is a passive antenna.

11. The system according to claim 6, characterized in that An antenna array is arranged between the outer arc and the inner arc on the front cross-sectional surface of the air-to-air antenna; the inner arc is the antenna back plate of the air-to-air antenna; The tangent slope of the arc between the first end point of the outer arc and the first inflection point is negative; the tangent slope of the arc between the first inflection point and the vertex of the outer arc is positive; and the tangent slope of the first inflection point is 0; The arc between the second end point of the outer arc and the second inflection point is symmetrical with the arc between the first end point of the outer arc and the first inflection point about the central axis; The arc between the second inflection point and the vertex of the outer arc is symmetrical with the arc between the first inflection point and the vertex of the outer arc about the central axis; the tangent slope of the second inflection point is 0.

12. A beam switching device, characterized in that: Applied to a processing unit, the device comprises: Trajectory monitoring module, used to monitor the movement trajectory of low-altitude terminals; A time determination module, used to determine the beam switching time of the low-altitude terminal under the composite antenna according to the motion trajectory of the low-altitude terminal; the composite antenna includes an air-to-air antenna and a ground-to-ground antenna, and an antenna backplane is arranged between the air-to-air antenna and the ground-to-ground antenna; A beam switching module is used to control the low-altitude terminal to perform beam switching according to the beam switching time; the beam switching means switching from the air-to-air beam of the air-to-air antenna to the ground-to-ground beam of the ground-to-ground antenna, or from the ground-to-ground beam of the ground-to-ground antenna to the air-to-air beam of the air-to-air antenna.

13. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 5 are implemented.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

15. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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