KR20100042710A - The structures for video telecommunication system of the uav(unmanned aerial vehicle) using wibro and adaptive vertical static beam-forming array antenna algorithm to overcome restriction of the altitude for uav - Google Patents

Abstract

PURPOSE: Structures for a video telecommunication system of a UAV(Unmanned Aerial Vehicle) using a WiBro and adaptive vertical static beam-forming array antenna algorithm to overcome restriction of the altitude for UAV are provided to estimate the arrival angle of the direction having high SNR(Signal to Ratio) by using an adaptive phase control algorithm. CONSTITUTION: A WiBro is applied as a communication system of unmanned aerial vehicles, and information is received continuously at a remote place. The image transmission and reception system of the unmanned aerial vehicle to which the WiBro is applied transmits and receives image information to and from the image transmission and reception system. An array antenna is applied to an aerial vehicle, and the SNR is maximized as a high antenna gain at an aerial altitude where a signal of a base station cell coverage hardly influences.

Description

Array structure of an unmanned aerial vehicle using WiBro and adaptive vertical static beam pattern forming antenna algorithm to overcome the unrestricted height of unmanned aerial vehicle using WiBro beam-forming array antenna algorithm to overcome restriction of the altitude for UAV}

WiBro Mobile Network, Communication System, Unmanned Aerial Vehicle, Array Antenna

Recently, the demand for civilian drones is increasing and the application of mobile communication system for video transmission and reception of UAV is required.

  The conventional unmanned aerial vehicle video transmission and reception system is composed of a VHF communication system and an antenna system. VHF method is more straight forward than UHF used in general data communication, maximum reach is 10km, and maximum communication speed is 10kbps, so it is suitable for visible distance UAV. In recent years, however, the demand for long-distance unmanned aerial vehicles has increased due to increased demand for civilian purposes such as environmental and forest fire surveillance, coastal surveillance, weather observation, remote sensing, GIS information collection, communication relay, air traffic control, smuggling and smuggling surveillance, and power line inspection. There is a need for a communication system that can check data in real time anywhere at any time, and is easily applicable, and a method of applying a low-cost mobile communication system is required.

Among commercial telecommunication systems, WiBro supports flexible handoff to ensure seamless data transmission and reception while moving, and provides high communication speed even in multipath channel environment based on OFDM technology. Therefore, WiBro, which guarantees excellent mobility and high speed data transmission, is suitable as an alternative to the communication system to be applied to the video transmission and reception system of UAV.

  However, in the construction of the UAV video transmission and reception system, the beam pattern of the WiBro base station antenna is directed toward the ground, so the UAV which is flying high due to the limitation of cell coverage has a sharp drop in the communication performance, which limits the altitude and transmits and receives high quality video. There was a bunch. Transceiver antennas mounted on the aircraft also generally use omnidirectional dipole antennas suitable for ground use, making it difficult for the antenna signals to reach the base station.

To solve this problem, there is a need for a method that can improve the reception rate and guarantee the QoS of the image by overcoming the altitude limitation without the real difficulty of replacing the antenna of the base station currently used or modifying the beam pattern of all the antennas in use. .

On the other hand, the beam pattern of the antenna formed by the array antenna can be sharpened to the desired pattern by adjusting the phase and the angle can also be adjusted. The present invention is an algorithm that can be expected to achieve excellent performance while being practically possible.

Recently, as the demand for civilian unmanned aerial vehicles increases, the application of a mobile communication system capable of high-speed data transmission and reception is required. However, it is composed of VHF-type communication system and antenna system applied to the existing unmanned aerial vehicle, which is more straight forward than UHF used in general data communication, the maximum reach is 10km, and the maximum communication speed is 10kbps, which is suitable for the UAV of visible distance. Therefore, it is not suitable for transmitting and receiving high speed data in long distance flight.

On the other hand, the base station of the current mobile communication system uses an antenna having an appropriate vertical / horizontal beam pattern according to the surrounding environment. In the case of a high-traffic microcell, the main beam is directed to the traffic-intensive area and the traffic is In the case of a small suburban macrocell, the beam pattern is adjusted so that the main beam is directed toward the cell edge. In addition, the beam pattern is adjusted using the antenna Tilt to increase coverage and reduce interference to other cells. However, since this is a horizontal beam pattern adjustment based on the mobile terminal on the ground, the unmanned aerial vehicle moving at a higher altitude than the base station on the ground is rather out of the beam pattern range of the base station antenna, so the communication performance is drastically deteriorated and high quality video is displayed. Difficulty sending and receiving, had to limit the altitude.

In addition, since the transmitting and receiving antennas mounted on the communication system of the aircraft generally use omnidirectional dipole antennas suitable for use on the ground, even if the transmitted signal is large, it is difficult for the signal to reach the base station.

There is a need for a solution to this problem, and there is a method of increasing the transmit / receive rate by introducing an adaptive array antenna system. This is a technique of adaptively forming a beam pattern at an angle with a large signal strength by estimating the angle of arrival in the direction of high signal-to-noise ratio (SNR) using an adaptive phase adjustment algorithm on an array antenna. However, this system has the disadvantages of high complexity, high computational complexity, and difficulty in realistic implementation.

WiBro mobile communication system is applied as a communication system for UAV. WiBro is based on Orthogonal Frequency Division Multiplexing (OFDM) to guarantee a high speed and stable data transmission environment and to enable various services. In particular, it effectively compensates for signal distortion due to Doppler spreading and multipath fading, enabling communication even in high-speed mobile environments, and supporting flexible handoff to ensure seamless data transmission and reception during movement. Therefore, Wibro, which guarantees this, can be used as an alternative to the UAV communication system.

  Also, in order to solve the problem of data transmission rate decrease and deviation from coverage according to flight altitude, adaptive phase adjustment is performed to replace the currently used base station antenna and to modify the beam pattern in the air direction or to predict the strength and direction of the signal from the base station. Instead of applying the algorithm, the array antenna is applied to the UAV's WiBro communication system, but based on the flight attitude information of the UAV, the beam pattern of the transmit / receive antenna is sharpened and adaptively always perpendicular to the ground. do.

By applying WiBro to communication systems such as video transmission and reception of unmanned aerial vehicles (UAV), wireless transmission and reception of data is possible without interruption.

In order to overcome the high limit of the unmanned aerial vehicle caused by the cell coverage formed by the beam pattern of the base station antenna facing the ground, 'Adaptive Vertical Fixed Beam Pattern Formation Array Antenna' is applied to achieve high reception and reliable data transmission and reception. Let's do it.

The structure of a UAV video transmission / reception system applying WiBro proposed in the present invention is shown in FIG.

As shown in FIG. 1, the system includes a flight control center (FCC), which is mounted on a UAV, and a ground control center (GCS), which is a ground control station.

The FCC consists of a camera unit, analog video signal receiver, video stream converter, central processor, GPS data receiver, WiBro connection, and WiBro modem, and converts the analog video signal obtained from the camera into a digital signal, encodes and compresses the GPS. Synthesize with GPS data obtained from the module. This data is sent through the WiBro modem to the WiBro network and forwarded to the GCS.

GCS is composed of FCC data access unit, central processing unit, video stream converting unit, image and data display unit located at remote location. It transmits various environmental variables and control information to FCC and receives image and GPS data transmitted from FCC screen. Output to.

<Table 1> shows the performance of UAV video transmission and reception system using WiBro.

Transmission Speed in UAV Video Transceiver System with WiBro A30m↘, V60km / h↘ Uplink (kbps) A30m↘, V60km / h↗ Uplink (kbps) 6.5 12.276 650 28.7 63.45 570 12.35 25.63 623 25.3 68.24 598 26.24 46.12 585 20.12 71.63 613 A30m↗, V60km / h↘ Uplink (kbps) A30m↗, V60km / h↗ Uplink (kbps) 42.5 52.056 216 38.1 79.074 194 43.2 45.756 204 35.8 128.178 226 39.2 41.562 346 43 68.22 188 A0m, V0km / h 1092 A0m, V60km / h 820

Where A is flight altitude and V is flight speed. The results were obtained through actual flight, and the communication performance varies depending on flight speed and flight altitude. It can be seen that this causes serious problems in operation in a video transmitting / receiving system that must guarantee an uplink speed of 1Mbps or more in order to smoothly transmit and receive an image of 352 x 288 pixel resolution at 20 frames / sec or more.

In order to solve this problem, UAV's WiBro modem is applied with an array antenna instead of a ground omni-directional antenna to sharpen the beam pattern of the transmit / receive antenna and to adapt it to the angle of the aircraft. A fixed beam pattern forming array antenna technique is introduced.

The array antenna applied here is an M x N plane antenna, which is composed of the structure of <Fig. 2>, and is represented by Equation 1.

,

은 각각 M 배열 소자들과 N 배열 소자들의 전류세기이며

,

는 위상지연 값이다.here

,

Are the current strengths of the M array elements and N array elements, respectively.

,

Is the phase delay value.

The basic concept of the adaptive vertical fixed beam pattern forming array antenna algorithm is shown in FIG. 3.

In this system, when the aircraft changes the rotation or altitude, the aircraft is inclined as shown in Fig. 4, and the angle of the main beam of the antenna is inclined out of the vertical direction by θ ', φ' by the angle α of the rolling and the angle β of the pitching.

The angle of the main beam formed by the array antenna is represented by Equation 2, and θ ₀ and φ ₀ are 0 degrees, respectively, to form an angle of the main beam perpendicular to the ground, and are inclined vertically by θ 'and φ'.

The detailed algorithm process is the same as the system of FIG.

 In the measuring device of FIG. 5, the angle of rolling and pitching that is changed when the UAV raises or rotates the flight altitude is measured using a gyro sensor and an accelerometer. This value can be converted to a value for changing the direction of the tilted main beam and then applied in reverse to correct it to be perpendicular to the ground again as shown in FIG. 6.

That is, α and β are angles at which the gas is inclined with respect to the aircraft measured through the measuring sensor in FIG. 5 and FIG. 6, which are angles for forming the beam pattern of the array antenna in phase compensation, θ ', The beam pattern is corrected to the main beam perpendicular to the ground by applying -θ 'and -φ' to the angle converted into φ 'to form the main beam. The angle conversion process is described by Equation 3 below.

As a result, the antenna's beam pattern is adaptively corrected to ensure that it is always perpendicular to the ground, even when the aircraft is constantly changing angles.

Unmanned aerial vehicles can check large amounts of data anytime, anywhere, in a wide range of long-distance areas, enabling environment and forest fire monitoring, coastal monitoring, weather observation, remote detection, GIS information collection, communication relay, air traffic control, smuggling and smuggling surveillance, and power line inspection. Scientific applications include environmental monitoring, meteorological and atmospheric data collection, oceanography data collection, agricultural monitoring, and geological mapping at high altitudes. This monitors using unmanned aerial vehicles without professional technical personnel, which has the industrial effect of saving labor costs and promoting the safety of professional technical personnel.

1: System structure for transmitting / receiving image information and GPS information to FCC (Flight Control Center) side of UAV mounted system and GCS (Ground Control Center) of remote ground control station

2: M x N plane array antenna structure used as a communication antenna of an unmanned aerial vehicle

Fig. 3: An algorithm of applying an array antenna to a communication system of an aircraft and adaptively correcting the direction of the main beam to keep the beam pattern perpendicular to the ground in order to overcome the limitation of flight altitude limited by the base station beam pattern cell coverage. Conceptual diagram

4 is a conceptual diagram showing that the direction of the main beam of the array antenna is greatly changed due to the angle of the rolling and pitching of the aircraft is changed when the aircraft is raised / lowered and rotated

FIG. 5 is a block diagram of an adaptive correction algorithm of an array antenna beam pattern. The angle of rolling and pitching that changes when an aircraft moves is measured and converted to an angle for forming an antenna beam, and then the angle of the main beam is corrected.

6: The beam pattern of the main beam is adaptively always applied by converting the angle of α, β that changes when the gas moves to θ ', φ' and then applying -θ ',-φ' to the angle forming the main beam. Conceptual diagram to correct the beam pattern perpendicular to the

Claims (5)

Applied to the communication system of the unmanned aerial vehicle, WiBro can be used to rescue information at high speed without remote data loss. System Structure for Aircraft (FCC) and Ground Station (GCS) for Transmitting / Receiving GPS Data and Compressed Video Information in WiBro's Video Transceiver System Application of array antenna to the aircraft to maximize signal-to-noise ratio (SNR) with high antenna gain even at high altitude where the signal of base station cell coverage is hardly increased to increase data rate and guarantee signal quality (QoS) High antenna gain by allowing the main beam's direction to be adaptively always perpendicular to the ground without using complex signal search algorithms (DOA estimation, MUSIC, etc.) when forming the beam pattern of the array antenna applied to the communication antenna of the aircraft Algorithm designed to improve communication performance The angle of inclination α, β of the aircraft with respect to the aircraft measured by the measuring sensor unit is converted to the angle of beam pattern formation of the array antenna in the phase correction unit, θ ', φ', and then -θ 'to the angle of forming the main beam. The formulas (Equations 3), <Fig. 5>, and <Fig. 6> for converting angles together with the method of correcting the beam pattern of the main beam to be always vertical to the ground by applying, -φ ' algorithm

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