Video transmission is to transmit video accurately and quickly from one place to another, which is anti-interference and clear in real time.
The unmanned aerial vehicle (UAV) video transmission system is an important part of unmanned aerial vehicle (UAV). It is a kind of wireless transmission equipment. With certain technology, the video captured by the camera carried by the field unmanned aerial vehicle (UAV) is wirelessly transmitted to ground control station in real time. Therefore, drone video transmitter is also known as the "eyes" of drones.
So, what is the current common drone wireless transmission technology? the mainstream technology of UAV video transmitting are the followings:
1、OFDM Technique
Technically, the most widely used transmission technology on the unmanned aerial vehicle is OFDM, which is a multi-carrier modulation, the technology is more suitable for high-speed data transmission, and OFDM has many advantages, for example, a large amount of data can be transmitted in a narrowband bandwidth, frequency selective fading or narrowband interference can be resisted and so on.
OFDM technique is mainly applied to application systems such as LTE (4G) and WIFI.
2，COFDM Technique
COFDM, i.e., coded OFDM, adds some channel coding (primarily adding error correction and interleaving) before OFDM modulation to improve system reliability. The difference between the COFDM and the OFDM is to add the error correction coding and the protection interval before the orthogonal modulation, so that the signal is transmitted more effectively. COFDM is currently most widely used in DVB (digital video broadcasting), DVB-T, DVB-S, DVB-C etc.
The COFDM (Orthogonal Frequency Division Multiplexing) modulation technology is the latest wireless transmission technology, which is a real multi-carrier technology, and the number reaches 1704 carrier (2K mode), even 8K mode, and really realizes high speed data transmission (2-20Mbps) of “anti-blocking” and “NLSO distance” in actual use and shows excellent “diffraction” and “penetration” performance.
COFDM technology is a better technology applied to wireless long range HD videos transmission of drone.
3，WIFI Technique
The data transmission of Wi-Fi transmission requires that the transmitting end and the receiving end first establish a communication handshake mechanism, and then each size is 512 bytes. The transmission of each data packet must be completed intact, and one byte in the data packet is lost to cause the entire data packet to be retransmitted, and the next data packet is transmitted only after the complete receiving of one data packet, which is the root cause of the transmission delay.
For drone flight, "real-time" wireless video transmission is crucial. Because of one byte, it is very time-consuming to retransmit the entire packet. Wi-Fi transmission is a high-speed wireless transmission technology. It is very easy to transmit and receive video in real time based on TCP/IP protocol, but the flight of drones requires high real-time performance. If the data packet is retransmitted, the operator cannot see the real-time video. Non-delayed real-time HD-video transmission are critical for operator.
The invention of Wi-Fi technology is not intended to be applied to "Air-to-Ground" transmission application scenarios. The two-way handshake mechanism makes it impossible to solve the distance and latency of UAV video transmission, so it cannot meet the needs of UAV video transmitting and receiving.
4，Lightbridge digital image transmission Technique
Lightbridge is a special communication link technology developed by DJI, which can transmit 720p high-definition video and display. The distance can usually reach 2 km, and more than 5 km (LOS).
Lightbridge technology uses one-way data transmission, which is like the transmission form of a high-level TV broadcasting tower. Compared with WIFI, it can reduce the video transmission delay, which is 2-3 times the WIFI transmission distance. It is mainly used in personal consumption drones such as DJI.
5，Simulation Transfer Techniques
Although there is almost no delay in analog data transmission, it is a one-way signal transmission technology, which is somewhat like the transmission of analog TV broadcast signals before the emergence of digital TV signals. When the signal weakens, there will be a snowflake screen, warning that the pilot should adjust the flight direction or fly back, closer to the return point.
The power consumption of analog data transmission is very large. When it wants to reach a long rang, its transmission power has exceeded the specified range. This technology has almost been eliminated in the application of Drone Video Transmitter.
Summary
Analysis shows that the OFDM technology and the COFDM technology are the mainstream of the Drone Transmitter, and COFDM technology is more advanced. Long Range Drone Video Transmitter is a balance between distance and power consumption, and further relates to a lot of modulation technologies, such as spread spectrum to improve anti-interference capability, channel information source technology optimization and so on.
COFDM technology product recommendation
Post time: Mar-09-2023