An Unmanned Aerial Vehicle Swarm Land-Air and Air-Air Communication System and Communication Method

Abstract

The present invention discloses a communication system and a communication method for an unmanned aerial vehicle (UAV) swarm in the air and between the air and the ground, including: a wingman UAV, an attendant UAV, and a ground base station. An air-to-air communication link is formed between the wingman UAV and the attendant UAV, and an air-to-ground communication link is formed between the wingman UAV and the ground base station. The air-to-air communication link uses ultraviolet (UV) LED scattered light communication; the air-to-ground communication link uses UV laser communication; in the air-to-ground communication link, the ground base station and the wingman UAV achieve the tracking function in combination with the closed-loop communication of the air-to-ground communication link. The present invention can establish stable air-to-ground and air-to-air communication links, realize the establishment of a communication link with a feedback mechanism between the base station and the wingman UAV, and will not be eavesdropped by non-intended communication objects. Moreover, the air-to-air communication link uses UV LED scattered light communication, and both the air-to-ground communication link and the air-to-air communication link use UV light for link communication. Utilizing the excellent confidentiality performance of UV light, the confidentiality of the communication system for the UAV swarm in the air and between the air and the ground is enhanced.

Description

Technical Field

[0001] The present invention relates to the field of ultraviolet communication for unmanned aerial vehicle (UAV) swarms, and particularly to a UAV swarm land-air and air-air communication system and a communication method. Background Art

[0002] In recent years, ultraviolet communication has attracted more and more attention due to its unique advantages. Ultraviolet communication is a kind of scattered light communication using the ultraviolet band in the atmospheric solar blind area, with advantages such as good confidentiality, low background noise, non-line-of-sight communication across obstacles, low power consumption of communication devices, and simple installation of communication devices. On the other hand, the shortcomings of traditional radio communication are becoming more and more obvious, specifically: being easily eavesdropped, scarce spectrum resources, being easily affected by obstacles, large power consumption of communication devices, and difficult installation of communication devices.

[0003] UAV swarms are highly flexible, maneuverable, and convenient for networking communication, so they have a wide range of applications in military, public, and civilian fields. At present, when UAV swarms communicate with each other, they still use the traditional radio method, which will lead to further congestion of the already scarce radio spectrum resources, and the radio communication signals are easily eavesdropped. Therefore, applying ultraviolet communication to UAV swarms can effectively avoid the above problems. At the same time, with the help of the maneuverability of UAVs, the advantages of ultraviolet networking communication can be better exerted. In application scenarios such as outdoor environments with harsh conditions and high-security communication requirements, it is difficult to apply traditional communication methods, and UAV swarm ultraviolet communication is an ideal communication method.

[0004] UAV swarm ultraviolet communication has advantages such as non-line-of-sight, strong confidentiality, strong flexibility, strong maneuverability, and convenient networking communication, so it has broad application prospects in military, public, and civilian fields. The communication link between the wingman (i.e., the leading aircraft) and the ground base station is called the land-air communication link. In the existing UAV swarm ultraviolet communication links, there are two types of land-air communication links. One is to use traditional communication such as radio, which will lead to the risk of the land-air communication link being eavesdropped; the other is to use ultraviolet LEDs for communication. Due to the limited effective communication distance of ultraviolet LEDs, this communication mode is not suitable for long-distance land-air link information transmission.

[0005] It should be noted that the information disclosed in the above background art section is only used for understanding the background of the present application, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0006] The purpose of the present invention is to solve the problem that the land-air and air-air communication of UAV swarms is easily eavesdropped, and to provide a UAV swarm land-air and air-air communication system and a communication method.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] An air-ground and air-air communication system for a drone swarm, comprising: wingmen drones, follower drones, and a ground base station. An air-air communication link is formed between the wingmen drones and the follower drones, and an air-ground communication link is formed between the wingmen drones and the ground base station; the air-air communication link uses ultraviolet LED scattered light communication; the air-ground communication link uses ultraviolet laser communication;

[0009] In the air-ground communication link, the ground base station and the wingmen drone achieve the tracking function in combination with the closed-loop communication of the air-ground communication link.

[0010] In some embodiments, the wingmen drone is equipped with a wingmen drone ultraviolet communication receiver, a wingmen drone ultraviolet LED communication transmitter, and a wingmen drone ultraviolet laser communication transmitter; the follower drone is equipped with a follower drone ultraviolet LED communication transmitter and a follower drone ultraviolet communication receiver; the ground base station includes a base station ultraviolet communication receiver and a base station ultraviolet laser communication transmitter.

[0011] In some embodiments, the alignment condition for the tracking function is to keep the transceiver within each other's field of view.

[0012] In some embodiments, the base station ultraviolet laser communication transmitter includes a laser three-axis turntable and an ultraviolet laser. The implementation of the tracking function includes the following steps:

[0013] S1. The wingmen drone reports its real-time position to the ground base station through the wingmen drone ultraviolet laser communication transmitter;

[0014] S2. The ground base station controls the laser three-axis turntable to scan the ultraviolet laser within the range of ±5° of the position reported by the wingmen drone, and at the same time transmits the information containing the position of the ground base station through the ultraviolet laser;

[0015] S3. If the wingmen drone ultraviolet communication receiver receives the information of the ground base station, it transmits the feedback information of successful reception to the ground base station through the wingmen drone ultraviolet laser communication transmitter until a stable air-ground communication link is successfully established.

[0016] In some embodiments, the field of view angles of the wingmen drone ultraviolet laser communication transmitter and the base station ultraviolet laser communication transmitter are 0-10°.

[0017] In some embodiments, for the situation where two or more wingmen drone ultraviolet communication receivers, follower drone ultraviolet communication receivers, or base station ultraviolet communication receivers receive signals simultaneously, the wingmen drone ultraviolet communication receiver, follower drone ultraviolet communication receiver, or base station ultraviolet communication receiver uses one of the following signal combination methods to receive signals: maximum ratio combining, equal gain combining, selection combining.

[0018] In some embodiments, the maximum ratio combining signal combining method includes weighting multiple channel signals of the wingman ultraviolet communication receiver, the follower ultraviolet communication receiver, or the base station ultraviolet communication receiver, and the weight value is determined by the ratio of the signal current to the noise after optoelectronic conversion of each channel; the equal gain combining signal combining method includes summing homogeneous signals based on the same weight; the selective combining signal combining method includes selecting the signal with the largest signal-to-noise ratio among all channels as the received signal, that is, the signal with the smallest noise variance or the signal to be selected according to the actual application scenario.

[0019] The present invention also provides a communication method for an air-ground communication link of a drone swarm, including:

[0020] The ground base station and the wingman combine to perform tracking and aiming through the closed-loop communication of the air-ground communication link. The tracking and aiming specifically include the following steps:

[0021] S1. The wingman reports its real-time position to the ground base station through the wingman ultraviolet laser communication transmitter;

[0022] S2. The ground base station controls the laser three-axis turntable in the base station ultraviolet laser communication transmitter to scan the ultraviolet laser in the base station ultraviolet laser communication transmitter within the range of a preset angle of the position reported by the wingman, and at the same time transmits the information containing the position of the ground base station through the ultraviolet laser;

[0023] S3. If the wingman ultraviolet communication receiver receives the information of the ground base station, it transmits the feedback information of successful reception to the ground base station through the wingman ultraviolet laser communication transmitter until a stable air-ground communication link is successfully established.

[0024] In some embodiments, step S3 includes the following steps:

[0025] A1. If the wingman does not receive the information of the ground base station, the ultraviolet laser increases the transmission power for scanning;

[0026] A2. If the base station ultraviolet communication receiver receives the feedback information of successful reception, the ultraviolet laser adaptively adjusts the transmission power according to the feedback information.

[0027] In some embodiments, the preset angle is ±5°.

[0028] The present invention has the following beneficial effects:

[0029] The present invention realizes the tracking function through the closed-loop communication of the ground base station and the wingman combined with the land-air communication link, can establish a stable air-air communication link, realizes the establishment of a communication link with a feedback mechanism between the base station and the wingman, and will not be eavesdropped by non-intended communication objects, solves the problem that the existing wireless communication technology in the land-air communication of the UAV swarm is easy to be eavesdropped, and the air-air communication link adopts ultraviolet LED scattered light communication, and both the land-air communication link and the air-air communication link use ultraviolet light for link communication, and utilizes the excellent confidentiality performance of ultraviolet light to enhance the confidentiality of the land-air and air-air communication systems of the UAV swarm. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the communication scenario of the ultraviolet land-air and air-air communication system of the UAV swarm in the embodiment of the present invention;

[0031] Figure 2 It is a schematic diagram of the structural composition of the ultraviolet land-air and air-air communication system of the UAV swarm in the embodiment of the present invention;

[0032] Figure 3 It is a structural composition diagram of the minimum communication unit for the ultraviolet land-air and air-air communication system of the UAV swarm in the embodiment of the present invention;

[0033] Figure 4 It is a schematic diagram of the non-line-of-sight scattered light communication channel model for the ultraviolet land-air and air-air communication system of the UAV swarm in the embodiment of the present invention;

[0034] Figure 5 It is a schematic diagram of the multi-transceiver non-line-of-sight scattered light communication channel model for the ultraviolet land-air and air-air communication system of the UAV swarm in the embodiment of the present invention;

[0035] Figure 6 It is a schematic diagram of the communication model in the ultraviolet laser line-of-sight communication scenario for the ultraviolet land-air and air-air communication system of the UAV swarm in the embodiment of the present invention;

[0036] Figure 7 It is a schematic diagram of the alignment conditions of the land-air link laser line-of-sight model for the ultraviolet land-air and air-air communication system of the UAV swarm in the embodiment of the present invention;

[0037] Figure 8 It is a flowchart of the establishment of the land-air communication link of the ultraviolet land-air and air-air communication system of the UAV swarm in the embodiment of the present invention;

[0038] Figure 9 It is a flowchart of the establishment and adaptive adjustment of the transmission power of the land-air communication link of the ultraviolet land-air and air-air communication system of the UAV swarm in the embodiment of the present invention;

[0039] Figure 10 It is a comparison data diagram of the ultraviolet light communication and radio communication ranges in the embodiment of the present invention;

[0040] The descriptions of the reference numerals are as follows:

[0041] 1 - wingman, 2 - ground communication base station, 3 - attendant aircraft, 101 - wingman ultraviolet communication receiver, 102 - wingman ultraviolet LED communication transmitter, 103 - wingman ultraviolet laser communication transmitter, 201 - base station ultraviolet communication receiver, 202 - base station ultraviolet laser communication transmitter, 301 - attendant aircraft ultraviolet communication receiver, 302 - attendant aircraft ultraviolet LED communication transmitter, 3011 - first attendant aircraft ultraviolet communication receiver, 3021 - first attendant aircraft ultraviolet LED communication transmitter, 3012 - second attendant aircraft ultraviolet communication receiver, 3022 - second attendant aircraft ultraviolet LED communication transmitter, 3013 - third attendant aircraft ultraviolet communication receiver, 3023 - third attendant aircraft ultraviolet LED communication transmitter, 1011 - photomultiplier tube / avalanche diode, 1012 - transimpedance amplifier, 1013 - digital-to-analog converter, 1014 - demodulator, 1015 - decoder, 1016 - memory, 2021 - base station encoder, 2022 - base station modulator, 2023 - laser driver, 2024 - ultraviolet laser, 2025 - laser three-axis turntable, 2026 - field of view angle adjustment device, 30201 - attendant aircraft encoder, 30202 - attendant aircraft modulator, 30203 - LED driver, 30204 - ultraviolet LED. Detailed implementation manners

[0042] The following gives a detailed description of the implementation manners of the present invention. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0043] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, the connection can be for a fixing function or for a coupling or communication function.

[0044] It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0045] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more such features. In the description of the embodiments of the present invention, the meaning of "a plurality" is two or more, unless otherwise specifically defined.

[0046] Embodiment

[0047] The ultraviolet air-ground and air-air communication system for a drone swarm provided by the embodiments of the present invention is used to solve the problem of poor communication confidentiality between the wingman drone and the ground base station.

[0048] The schematic diagram of the ultraviolet air-ground and air-air communication scenario provided by the embodiments of the present invention is as Figure 1 and Figure 2 shown, including: wingman drone 1, follower drone 3, and ground communication base station 2.

[0049] The wingman drone is equipped with a wingman ultraviolet communication receiver 101, a wingman ultraviolet LED communication transmitter 102, and a wingman ultraviolet laser communication transmitter 103. In the embodiments of the present invention, the wingman drone 1 has two wingman ultraviolet communication receivers 101.

[0050] The follower drone is equipped with a follower ultraviolet LED communication transmitter 302, a follower ultraviolet communication receiver 301, etc.; for example: the first follower ultraviolet communication receiver 3011, the first follower ultraviolet LED communication transmitter 3021, the second follower ultraviolet communication receiver 3012, the second follower ultraviolet LED communication transmitter 3022, the third follower ultraviolet communication receiver 3013, and the third follower ultraviolet LED communication transmitter 3023.

[0051] The ground communication base station includes a base station ultraviolet communication receiver 201 and a base station ultraviolet laser communication transmitter 202.

[0052] In the embodiments of the present invention, the wingman drone 1 and the follower drone 3 perform scattered light communication through LEDs, forming an air-air communication link; the wingman drone 1 and the ground communication base station 2 communicate through ultraviolet lasers, forming an air-ground communication link.

[0053] For the air-to-air communication link, i.e., between the wingman and the follower aircraft, ultraviolet LED scattered light communication is adopted; for the air-to-ground communication link, i.e., between the wingman and the ground base station, ultraviolet laser communication is adopted. In application scenarios such as outdoor areas with harsh environments and high-security communication requirements, it is difficult to apply traditional communication methods. Ultraviolet communication for UAV swarms is an ideal communication method. In the embodiment of the present invention, the laser three-axis turntable and the ultraviolet laser in the ultraviolet laser communication transmitter of the base station can achieve the tracking function in combination with the closed-loop communication of the air-to-ground communication link, and stable air-to-ground and air-to-air communication links can be established. The communication mode of the embodiment of the present invention can effectively eliminate the risk of wiretapping of the air-to-ground communication link, ensure both the information security of the air-to-air and air-to-ground communication links, and effectively guarantee the transmission quality of information.

[0054] In the embodiment of the present invention, the ultraviolet communication receiver 101 of the wingman, the ultraviolet communication receiver 301 of the follower aircraft, and the ultraviolet communication receiver 201 of the base station are used to convert the received ultraviolet light signal into an electrical signal, which is mainly composed of a photomultiplier tube or an avalanche diode, a transimpedance amplifier, a digital-to-analog converter, a demodulator, a decoder, a memory, etc.

[0055] In the embodiment of the present invention, the ultraviolet LED communication transmitter of the wingman and the ultraviolet LED communication transmitter of the follower aircraft are used to emit the information to be transmitted through the LED, which mainly includes an encoder, a modulator, an LED driver, an ultraviolet LED, etc.

[0056] In the embodiment of the present invention, the ultraviolet laser communication transmitter of the wingman and the ultraviolet laser communication transmitter of the base station are used to emit the information to be transmitted in the form of laser, including an encoder, a modulator, a laser driver, an ultraviolet laser, a laser three-axis turntable, a field of view angle adjustment device, etc.

[0057] The field of view angle adjustment device is composed of a laser beam expander, a concave lens group, a lens position moving device, etc.

[0058] Refer to Figure 3 , the structural composition diagram of the minimum communication unit composed of the ultraviolet LED communication transmitter of the follower aircraft, the ultraviolet laser communication transmitter of the base station, and the ultraviolet communication receiver of the wingman. This minimum communication unit is applicable to the situation where the follower aircraft and the ground communication base station simultaneously transmit signals to the wingman, including the ultraviolet LED communication transmitter 302 of the follower aircraft, the ultraviolet communication receiver 101 of the wingman, and the ultraviolet laser communication transmitter 202 of the base station.

[0059] For the random follower UV LED communication transmitter 302, according to the sequence of signal processing, first, the information to be transmitted is encoded by the random follower encoder 30201, then the signal is transferred to the random follower modulator 30202 and modulated by modulation methods such as OOK, PPM, OFDM, etc. After that, the modulated signal is input into the LED driver 30203, and the LED driver 30203 controls the UV LED 30204 to emit the signal.

[0060] For the base station UV laser communication transmitter 202, according to the sequence of signal processing, first, the information to be transmitted is encoded by the base station encoder 2021, then the signal is transferred to the base station modulator 2022 and modulated by modulation methods such as OOK (binary amplitude shift keying), PPM (pulse position modulation), DPPM (differential pulse position modulation), etc. After that, the modulated signal is input into the laser driver 2023, and the laser driver controls the UV laser 2024 to emit the signal. In addition, the azimuth angle of the laser emission is controlled by the laser three-axis turntable 2025, so as to realize the tracking and aiming of the base station UV laser communication transmitter at the wingman; the field of view angle of the UV laser emission beam is expanded by the field of view angle adjustment device 2026. To ensure the confidentiality of the land-air communication link, the maximum field of view angle does not exceed 10°, so as to ensure that the wingman UV communication receiver on the wingman can effectively receive the information.

[0061] For the wingman UV communication receiver 101, according to the sequence of signal processing, first, the received signal is photoelectrically converted by the photomultiplier tube / avalanche diode 1011, and the output signal is a current signal. After that, it is converted into a voltage signal and amplified by the transimpedance amplifier 1012. Subsequently, the voltage signal is digitally sampled by the analog-to-digital converter 1013. After that, the signal passes through the demodulator 1014 and the decoder 1015 in sequence to restore the original information. Finally, the restored information is imported into the memory 1016 for storage for subsequent information processing.

[0062] Refer to Figure 4 , for the UV LED scattered light communication in the non-line-of-sight situation, the optical power formulas received by the wingman UV communication receiver and the random follower UV communication receiver are as follows:

[0063]

[0064] Among them, P t is the optical power at the transmitting end, K e is the atmospheric extinction coefficient, K e = K a + K s , K a is the atmospheric absorption coefficient, K s is the atmospheric scattering coefficient, A r is the receiving area, φ Ris the receiving field of view angle, φ T is the transmitting field of view angle, θ R is the receiving elevation angle, θ T is the transmitting elevation angle, P r is the received optical power, P s is the scattering phase function, and d is the distance between the receiving end and the transmitting end.

[0065] In the embodiment of the present invention, the non-line-of-sight scattered optical communication channel models of two transceiver ends of the ultraviolet light land-air and air-air communication system for the unmanned aerial vehicle group are as Figure 5 shown. In the figure, T1 and T2 respectively represent the first and the second transmitting ends, and R1 and R2 respectively represent the first and the second receiving ends. θ T1 and θ T2 respectively represent the field of view angles of the first and the second transmitting ends, θ R1 and θ R2 respectively represent the field of view angles of the first and the second receiving ends, α T1 and α T2 respectively represent the elevation angles of the first and the second transmitting ends, α R1 and α R2 respectively represent the elevation angles of the first and the second receiving ends. For the ultraviolet LED non-line-of-sight scattered optical communication with multiple transceiver ends, in the case of using OOK intensity modulation, the signals received by each wingman ultraviolet communication receiver, follower ultraviolet communication receiver or base station ultraviolet communication receiver can be written as:

[0066]

[0067] where Z represents the interference term, η is the optoelectronic conversion coefficient, P i is the optical power of the i-th transmitting end received by the receiving end, i ∈ [1, N] represents the serial number of the transmitting end, s i ∈ {0, 1} represents the OOK modulation symbol, N is the number of transmitting ends, w is the additive Gaussian white noise with zero mean, and its variance f is the carrier frequency, h is the Planck constant, and R is the bandwidth of the communication system; here, since the background noise of ultraviolet light can be ignored and the thermal noise dominates, this noise is described by the Gaussian distribution.

[0068] For the case where two or more wingman ultraviolet communication receivers, follower ultraviolet communication receivers or base station ultraviolet communication receivers receive signals simultaneously, the wingman ultraviolet communication receiver, follower ultraviolet communication receiver or base station ultraviolet communication receiver receives signals by using one of the following signal combination methods: maximum ratio combining, equal gain combining, selective combining.

[0069] For the case where two wingman UV communication receivers, follower UV communication receivers, or base station UV communication receivers receive signals simultaneously, let the signals of their UV communication receivers be y1 and y2 respectively, and the noise variances be and The received signals can adopt one of three different combination methods: maximum ratio combining, equal gain combining, and selection combining;

[0070] The maximum ratio combining signal combination weights multiple channel signals of the wingman UV communication receiver, follower UV communication receiver, or base station UV communication receiver, and the weight value is determined by the ratio of the signal current to the noise after photoelectric conversion of each channel.

[0071] The received signal y can be expressed as:

[0072]

[0073] The equal gain combining signal combination method sums homogeneous signals based on the same weight. The received signal can be expressed as:

[0074] y = (y1 + y2) / 2

[0075] Selection combining can be to select the signal with the largest signal-to-noise ratio among all channels as the received signal, that is, the signal with the smallest noise variance, or the signal to be selected can be set according to the actual application scenario.

[0076] The schematic diagram of the communication model in the UV laser line-of-sight communication scenario in the embodiment of the present invention is as Figure 6 shown, β t is the half-angle of the light beam at the transmitting end, ξ is the distance between the receiving end and the transmitting end, β is the angle between the photon transmission direction and the positive y-axis direction, σ is the half-angle of the light beam at the receiving end, τ t is the distance from the transmitting end to the plane where the receiving surface is located, τ r is the distance from the receiving end to the plane where the receiving surface is located, ∈ is the angle between the photon transmission direction and the positive y-axis direction during secondary scattering, θ is the angle between the photon secondary scattering direction and the primary scattering direction, β R is the half-angle of the light beam at the receiving end. The photons reaching the receiver are divided into two categories: one is the directly reaching photons; the second is the photons reaching after one scattering. According to the photon type, their energies can be deduced respectively. The directly received light energy: Assume that the effective area of the circular receiver is A r , then the directly received half-angle of the light beam σ = tan -1 [(A r / π) 1 / 2 / ξ], where ξ is the distance from the transmitting end to the receiving end.

[0077] The receiver is divided into concentric rings. According to the theory of ultraviolet light propagation, the light energy received within the annular micro-element surface is as follows:

[0078]

[0079] where E t is the light energy emitted by the transmitting end, k e is the extinction coefficient, which is the sum of the scattering coefficient k s and the absorption coefficient k a . β is the angle between the photon propagation direction and the positive y-axis direction. ω t = 2π(1 - cosβ t ) is the solid cone angle of the transmitting end; β t is the half-angle of the light beam at the transmitting end, and ξ is the distance between the receiving end and the transmitting end. The area element ds = 2π(ξtanβ)d(ξtanβ) = 2πξ 2 tanβsec 2 βdβ.

[0080] Integrating the received energy element over the entire area of the receiving surface, the directly received light energy can be obtained:

[0081]

[0082] Scattered received light energy: Assume that photons reach the receiver after one scattering. The energy of photons not absorbed within the micro-element volume is:

[0083]

[0084] where τ t is the distance from the transmitting end to the plane where the receiving surface is located, and τ r is the distance from the receiving end to the plane where the receiving surface is located.

[0085] The light energy emitted from the micro-element volume and received by the receiver is:

[0086]

[0087] where τ r is the distance from the receiving end to the plane where the receiving surface is located, k s is the atmospheric scattering coefficient of ultraviolet light, is the phase scattering function, β max is the maximum value of the angle between the photon propagation direction and the positive y-axis direction, and ∈ is the angle between the photon propagation direction and the positive y-axis direction during secondary scattering.

[0088] Phase scattering function is the weighted sum of the Rayleigh scattering and Mie scattering phase functions:

[0089]

[0090]

[0091]

[0092] wherein is the Rayleigh scattering coefficient, is the Rayleigh scattering phase function, is the Mie scattering phase function, is the Mie scattering coefficient, and there is γ, g, f are model parameters. Generally, γ = 0.017, f = 0.5, and g = 0.72 are taken.

[0093] The energy received by the final receiving end is the sum of the direct received energy and the once-scattered received energy. The path loss can be obtained from the ratio of the received energy to the transmitted energy.

[0094] In the embodiment of the present invention, the alignment condition of the tracking function of the land-air link laser line-of-sight model is as Figure 7 shown. In an actual UAV ultraviolet communication system, due to the small path loss of line-of-sight transmission, it is only necessary to keep the transceiver within each other's field of view angles, rather than strictly aligning the transceiver. According to the geometric relationship as Figure 7 shown, the alignment condition for the LOS (line-of-sight) communication mode is:

[0095] σ T = arccos(cosθ T cosα T ) < β T

[0096] σ R = arccos(cosθ R cosα R ) < β R

[0097] where σ T is the angle between the axis of the transmitter's field of view and the connection line between the transceiver, σ R is the angle between the axis of the receiver's field of view and the connection line between the transceiver, θ T is the angle between the axis of the transmitter's field of view and the projection line of the transmitter's axis on the XOY plane, θ R is the angle between the axis of the receiver's field of view and the projection line of the receiver's axis on the XOY plane, α T is the angle between the projection line of the transmitter's axis on the XOY plane and the connection line between the transceiver, α R is the angle between the projection line of the receiver's axis on the XOY plane and the connection line between the transceiver, β T is the half-angle of the transmitter's light beam, βR is the half-angle of the light beam at the receiving end. This alignment condition can be used for configuring the transceiver geometry of a land-air communication link based on laser line-of-sight communication.

[0098] The flowchart for establishing the land-air communication link of the ultraviolet light land-air and air-air communication system for a drone swarm in an embodiment of the present invention is as Figure 8 shown. First, the wingman reports its real-time position to the ground base station through the wingman ultraviolet laser communication transmitter. Then, the ground base station controls the laser three-axis turntable to scan within a preset angle range of the position reported by the wingman. In this embodiment, the preset angle is ±5°. At the same time, the ground base station transmits the information containing its own position through the ultraviolet laser. If the wingman ultraviolet communication receiver receives the information from the ground base station, it transmits the feedback information of successful reception to the ground base station through the wingman ultraviolet laser communication transmitter on the wingman until a stable land-air communication link is successfully established. Combining the above process, the laser three-axis turntable can realize the tracking function in combination with the closed-loop communication of the land-air communication link.

[0099] In some other embodiments, the flowchart for establishing and adaptively adjusting the transmission power of the land-air communication link of the ultraviolet light land-air and air-air communication system for a drone swarm is as Figure 9 shown. First, the wingman reports its real-time position to the ground base station through the wingman ultraviolet laser communication transmitter. Then, the ground base station controls the laser three-axis turntable to scan within a range of ±5° of the preset angle of the position reported by the wingman. At the same time, the ground base station transmits the information containing its own position through the ultraviolet laser. If the wingman receives the information from the ground base station, it transmits the feedback information of successful reception to the ground base station through the wingman ultraviolet laser communication transmitter on the wingman, and the feedback information includes the transmission power value. If the wingman does not receive the information from the ground base station, the ultraviolet laser of the ground base station increases the transmission power. The ground base station then controls the laser three-axis turntable again to scan within a range of ±5° of the position reported by the wingman, and at the same time transmits the information containing its own position through the ultraviolet laser. If the wingman receives the information from the ground base station, it transmits the feedback information of successful reception (the feedback information includes the transmission power value) to the ground base station through the wingman ultraviolet laser communication transmitter on the wingman. If the base station ultraviolet communication receiver of the ground base station does not receive the feedback information, the wingman ultraviolet laser communication transmitter on the wingman continues to transmit the feedback information of successful reception to the ground base station. If the base station ultraviolet communication receiver of the ground base station receives the feedback information, the ultraviolet laser of the ground base station adaptively adjusts the transmission power according to the feedback information until a stable land-air communication link is successfully established. The output power range of the ultraviolet laser is 1 mW - 1000 mW, and the linear adjustment of the output power can be realized through the output power control module. The initial value of the luminous power of the lasers of the wingman and the ground base station is 20 mW.

[0100] The ultraviolet communication of the UAV swarm has specific application scenarios, that is, confidentiality is required. The beneficial effect of the embodiment of the present invention is mainly the confidentiality of the land-air communication link. For the proof of the beneficial effect in the embodiment of the present invention, the simulation results of the ultraviolet light communication and the radio communication range are compared as Figure 10 shown. For electromagnetic wave communication, the transmission loss PL EMW between two ideal point source antennas in free space is:

[0101] PL EMW = 32.45 + 20lg f + 20lg d

[0102] where f is the frequency of the radio used, which is taken as 800Mhz in the simulation; d is the communication distance.

[0103] For the path loss of ultraviolet light communication, the Monte Carlo simulation method is used for simulation. The number of simulated photons is one million, the number of photon scattering times is single scattering, the communication distance is 10,000 meters, the pitch angle and off-axis of the transceiver are both 0°, the field of view angle is 60°, and the other parameters required for the simulation are the same as those mentioned above in the embodiment of the present invention. The simulation results are as Figure 10 shown. If the path loss exceeds 100dB, the communication quality is considered extremely poor. It can be concluded that the effective communication distance of ultraviolet light communication is about 57 meters, while the distance of radio communication is 3000 meters. Therefore, the communication confidentiality of ultraviolet light communication is better than that of radio communication. Since the light emitted by the ultraviolet LED is Lambertian distribution, the ultraviolet LED optical communication can achieve small-range air-air link secure communication.

[0104] Many research teams at home and abroad have successfully achieved long-distance laser communication. Among the published research results, the farthest laser communication link successfully achieved is 40,000km, and the farthest ultraviolet laser communication link successfully achieved is 50km. Similarly, in the embodiment of the present invention, for the land-air communication link that requires long-distance communication, for the problem of large path loss of ultraviolet light communication, the signal strength received by the receiving end can be improved by increasing the transmission power. The power of the ultraviolet laser is larger than that of the ultraviolet LED. In addition, due to the good collimation of the laser, the field of view angle of the ultraviolet laser is much smaller than that of the ultraviolet LED, and the energy emitted by it is more concentrated within the field of view of the ultraviolet laser.

[0105] In the embodiment of the present invention, the field of view angles of the base station ultraviolet laser communication transmitter and the wingman ultraviolet laser communication transmitter are controlled within the range of 0-10°. Therefore, a larger transmission energy can be concentrated within a smaller field of view, so as to achieve long-distance land-air link communication. Since most of the photons of ultraviolet laser communication are line-of-sight propagation, effective communication can be achieved only when the field of view angle of the receiving end is within the field of view angle of the ultraviolet laser.

[0106] Combined with the laser three-axis turntable tracking function of the embodiments of the present invention, a communication link with a feedback mechanism can be established between the base station ultraviolet laser communication transmitter and the wingman, and it will not be eavesdropped by non-intended communication objects. Therefore, the embodiments of the present invention can achieve better long-distance land-air link secure communication.

[0107] For radio communication, its communication signals will spread over a large range. As long as the eavesdropper is within this range, the communication signals will be eavesdropped. However, the collimation of laser is better. When using ultraviolet laser for land-air communication, the signals will not spread over a large range. Effective communication can be achieved only when the field of view angle of the receiving end is within the field of view angle of the ultraviolet laser. The field of view angles of the base station ultraviolet laser communication transmitter and the wingman ultraviolet laser communication transmitter in the embodiments of the present invention are adjustable. To ensure the confidentiality of the land-air communication link, the field of view angles of the base station ultraviolet laser communication transmitter and the wingman ultraviolet laser communication transmitter are controlled within the range of 0-10°. Therefore, compared with radio communication, the confidentiality of the embodiments of the present invention is better than that of radio communication, and it is applicable to fields such as secure communication, outdoor multi-obstacle environment, and emergency communication.

[0108] In the fields of secure communication and emergency communication, compared with radio communication, it has the following beneficial effects:

[0109] 1) The embodiments of the present invention can achieve secure emergency communication in outdoor areas with harsh environments. The shortcomings of traditional radio communication are obvious, specifically: being easily eavesdropped, scarce spectrum resources, being easily affected by obstacles, high power consumption of communication devices, difficult erection of communication devices, etc. However, the ultraviolet communication means of the drone swarm can make up for these defects.

[0110] 2) The embodiments of the present invention can achieve non-line-of-sight communication across obstacles, and at the same time can ensure the security of the land-air and air-air communication links and the practicability of data transmission. Ultraviolet light communication uses the ultraviolet band of the atmospheric solar blind area for scattered light communication, and has advantages such as good confidentiality, low background noise, being able to cross obstacles for non-line-of-sight communication, low power consumption of communication devices, and simple erection of communication devices.

[0111] In application scenarios such as outdoor areas with harsh environments and applications requiring high-security communication, it is difficult to apply traditional communication methods. The ultraviolet communication of the drone swarm is an ideal communication method. The embodiments of the present invention have unique advantages such as non-line-of-sight, good confidentiality, and stable communication link, and are irreplaceable in some fields.

[0112] The method provided by the embodiments of the present invention belongs to the field of ultraviolet light communication of drone swarms. This field requires communication methods to have high security. Aiming at the problem that the land-air communication link of the current ultraviolet communication system of drone swarms faces the risk of being eavesdropped, a land-air and air-air communication system for drone swarms is proposed.

[0113] The method of this embodiment can effectively eliminate the risk of wiretapping of the land-air communication link compared with existing similar methods, which can not only ensure the information security of the air-air and land-air communication links, but also effectively ensure the transmission quality of information. It can lay a solid foundation for the application of ultraviolet communication technology in unmanned systems.

[0114] The pain points to be solved are as follows:

[0115] In the current ultraviolet communication system for unmanned aerial vehicle (UAV) swarms, the communication between the wingman, i.e., the leading aircraft, and the ground base station still uses radio communication, which will lead to the risk of wiretapping of the land-air communication link. The method of this embodiment combines LED scattered light communication and laser line-of-sight communication, which can effectively solve the problem of communication security of the land-air communication link.

[0116] The communication mode of the embodiment of the present invention can effectively eliminate the risk of wiretapping of the land-air communication link, which can not only ensure the information security of the air-air and land-air communication links, but also effectively ensure the transmission quality of information.

[0117] The embodiment of the present invention combines a laser three-axis turntable, which can realize the tracking function in combination with the closed-loop communication of the land-air communication link, and can establish a stable land-air and air-air communication link.

[0118] The specific application scenarios are as follows:

[0119] It can realize the ultraviolet communication of UAV swarms with high confidentiality, and can be provided for scientific research projects or practical applications such as scientific research institutes, R & D institutions, commercial companies, government agencies, etc., such as: confidential communication means for outdoor activities, emergency communication in areas with complex terrain, emergency communication in strong-scattering bad weather, and confidential emergency communication in areas such as mountains and deserts where radio frequency communication is not supported.

[0120] The method of this embodiment has great application prospects and has the following market value in the fields of confidential communication and emergency communication:

[0121] 1) The method of this embodiment can realize confidential emergency communication in outdoor areas with harsh environments. The shortcomings of traditional radio communication are obvious, specifically: being easily wiretapped, scarce spectrum resources, being easily affected by obstacles, large power consumption of communication devices, difficult erection of communication devices, etc., while the ultraviolet communication means of UAV swarms can make up for these defects.

[0122] 2) The method of this embodiment can realize non-line-of-sight communication by bypassing obstacles, and at the same time can ensure the security of the land-air and air-air communication links and the practicability of data transmission. Ultraviolet light communication uses the ultraviolet band of the atmospheric sun-blind area for scattered light communication, which has the advantages of good confidentiality, low background noise, being able to bypass obstacles for non-line-of-sight communication, low power consumption of communication devices, and simple erection of communication devices.

[0123] The method of this embodiment has unique advantages such as non-line-of-sight, good confidentiality, and stable communication link, and is irreplaceable in some fields.

[0124] The method of this embodiment can be applied to various outdoor environments that require secure communication in the future, and has great application prospects in civil, public, military and other fields. In the future, this technology will continue to be prototyped and the technical theory will be continuously enriched to promote the application of UAV swarm ultraviolet communication technology in multiple fields in China as soon as possible, and improve the technical level of secure communication and emergency communication in China.

[0125] The above content is a further detailed description of the present invention in combination with specific / optimal embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several alternatives or modifications can be made to these described embodiments, and these alternative or modified forms should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "preferred embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. Without conflict, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the scope of the patent application.

Claims

1. An air-ground and air-air communication system for a swarm of unmanned aerial vehicles, characterized in that, Including: A wingman aircraft, a follower aircraft, and a ground base station. An air-to-air communication link is formed between the wingman aircraft and the follower aircraft, and a land-to-air communication link is formed between the wingman aircraft and the ground base station. The air-to-air communication link uses ultraviolet LED scattered light communication, and the land-to-air communication link uses ultraviolet laser communication. In the land-to-air communication link, the ground base station and the wingman aircraft achieve a tracking function through the closed-loop communication of the land-to-air communication link. The wingman aircraft is equipped with a wingman ultraviolet communication receiver, a wingman ultraviolet LED communication transmitter, and a wingman ultraviolet laser communication transmitter. The follower aircraft is equipped with a follower ultraviolet LED communication transmitter and a follower ultraviolet communication receiver. The ground base station includes a base ultraviolet communication receiver and a base ultraviolet laser communication transmitter. The base ultraviolet laser communication transmitter includes a laser three-axis turntable and an ultraviolet laser. Among them, the wingman aircraft reports its real-time position to the ground base station through the wingman ultraviolet laser communication transmitter. The ground base station controls the laser three-axis turntable to scan the ultraviolet laser within the range of ±5° of the position reported by the wingman aircraft, and at the same time transmits the information containing the position of the ground base station through the ultraviolet laser. If the wingman ultraviolet communication receiver receives the information of the ground base station, it will transmit the feedback information of successful reception to the ground base station through the wingman ultraviolet laser communication transmitter until a stable land-to-air communication link is successfully established. Among them, if the wingman aircraft does not receive the information of the ground base station, the ultraviolet laser increases the transmission power for scanning. If the base ultraviolet communication receiver receives the feedback information of successful reception, the ultraviolet laser adaptively adjusts the transmission power according to the feedback information. Among them, the geometric structure of the transceiver of the land-to-air communication link based on laser line-of-sight communication is configured according to the alignment conditions of the tracking function of the land-to-air link laser line-of-sight model. The alignment conditions of the LOS (line-of-sight) communication mode are: σ T = arccos(cosθ T cosα T ) < β T σ R = arccos(cosθ R cosα R ) < β R where σ T is the angle between the emitter field of view axis and the line connecting the transceiver, σ R is the angle between the receiver field of view axis and the line connecting the transceiver, θ T is the angle between the emitter field of view axis and the projection line of the emitter axis on the XOY plane, θ R is the angle between the receiver field of view axis and the projection line of the receiver axis on the XOY plane, α T is the angle between the projection line of the emitter axis on the XOY plane and the line connecting the transceiver, α R is the angle between the projection line of the receiver axis on the XOY plane and the line connecting the transceiver, β T is the half-angle of the light beam at the emitter, β R is the half-angle of the light beam at the receiver.

2. The UAV swarm land-air and air-air communication system according to claim 1, characterized in that The alignment condition of the tracking function is to keep the transceiver within each other's field of view.

3. The UAV swarm land-air and air-air communication system according to claim 1, wherein, The field of view of the wingman ultraviolet laser communication transmitter and the base ultraviolet laser communication transmitter is 0 - 10°.

4. The UAV swarm land-air and air-air communication system according to claim 1, wherein For the situation where two or more wingman ultraviolet communication receivers, follower ultraviolet communication receivers, or base ultraviolet communication receivers receive signals simultaneously, the wingman ultraviolet communication receiver, follower ultraviolet communication receiver, or base ultraviolet communication receiver uses one of the following signal combination methods to receive signals: maximum ratio combining, equal gain combining, selection combining.

5. The UAV swarm land-air and air-air communication system according to claim 4, wherein The maximum ratio combining signal combination method includes weighting the multiple channel signals of the wingman ultraviolet communication receiver, follower ultraviolet communication receiver, or base ultraviolet communication receiver, and the weight value is determined by the ratio of the signal current to the noise after the optoelectronic conversion of each channel. The equal gain combining signal combination method includes summing homogeneous signals based on the same weight. The selection combining signal combination method includes selecting the signal with the largest signal-to-noise ratio among all channels as the received signal, that is, the signal with the smallest noise variance or the signal to be selected according to the actual application scenario.

6. A communication method for the land-air communication link of a drone swarm, using the land-air and air-air communication system for drone swarms as described in any one of claims 1 to 5, characterized in that, The method includes: The ground base station and the wingman aircraft perform tracking through the closed-loop communication of the land-to-air communication link. The specific tracking includes the following steps: S1. The wingman reports its real-time position to the ground base station through the wingman ultraviolet laser communication transmitter. S2. The ground base station uses the laser three-axis turntable in the base station ultraviolet laser communication transmitter to make the ultraviolet laser in the base station ultraviolet laser communication transmitter scan within the range of ±5° of the position reported by the wingman, and at the same time transmits the information containing the position of the ground base station through the ultraviolet laser. S3. If the wingman ultraviolet communication receiver receives the information of the ground base station, it transmits the feedback information of successful reception to the ground base station through the wingman ultraviolet laser communication transmitter until a stable land-air communication link is successfully established; among them, if the wingman does not receive the information of the ground base station, the ultraviolet laser increases the transmission power for scanning; if the base station ultraviolet communication receiver receives the feedback information of successful reception, the ultraviolet laser adaptively adjusts the transmission power according to the feedback information.

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