What are the commonly used UAV image transmission technologies?
The UAV image transmission system is an important part of the UAV. It is a kind of wireless electronic transmission equipment that uses certain technology to wirelessly transmit the video captured by the on-site UAV camera to the remote rear in real time. Therefore, UAV image transmission is also called the "eyes" of UAVs.
The current mainstream technology of UAV image transmission:
1, OFDM technology
Technically, the most widely used transmission technology on drones is OFDM, which is a type of multi-carrier modulation. This technology is more suitable for high-speed data transmission. OFDM has many advantages, such as the ability to transmit even under narrow bandwidth. A large amount of data, able to combat frequency selective fading or narrowband interference, and so on. However, OFDM also has shortcomings: (1) carrier frequency offset; (2) very sensitive to phase noise and carrier frequency offset; (3) relatively high peak-to-average ratio. Therefore, it is the perfect technology to solve these three flaws and bottlenecks.
2, COFDM technology
COFDM is coded OFDM. Some channel coding (mainly to increase error correction and interleaving) is added before OFDM modulation to improve the reliability of the system. The difference between COFDM and OFDM is that error correction coding and guard interval are added before orthogonal modulation, so that the signal can be transmitted more effectively. OFDM is mainly used in application systems such as LTE (4G) and WIFI.
3, WIFI technology
WiFi transmission is the most widely used technology for UAV image transmission with high cost performance. However, because WiFi has many technical limitations and cannot be modified, and many manufacturers use solutions to build directly, its shortcomings are also very prominent. : For example, what format the chip is designed into is what format, cannot be modified, the technology is relatively solid; the real-time performance of interference management strategies is not strong; the channel utilization rate is relatively low, etc.
4, Lightbridge high-definition long-distance digital image transmission technology
Lightbridge technology uses one-way image data transmission, similar to the data transmission form of a television broadcasting tower located at a high altitude. The data transmission of Wi-Fi image transmission requires the sending end and the receiving end to first establish a communication handshake mechanism, and then transmit each data packet with a size of 512 bytes. After confirming the complete reception of a data packet, the transmission of the next data packet is started, and this is the root cause of the image transmission delay.
5. Analog image transmission technology
Some UAVs without pan/tilt cameras can reach speeds of up to 80 km/h and use analog signal transmission technology. There is almost no delay in analog image transmission, and another feature of analog image transmission is that when the limit distance is reached, there will be no sudden screen jam or complete loss of the entire picture. Analog video transmission is also a one-way signal transmission technology, which is a bit similar to the transmission of analog TV broadcast signals before the digital TV signal appears. When the signal becomes weak, a snowflake screen will appear, warning the pilot to adjust the flight direction or go back. Fly, get closer to the home point.
It can be said that the two image transmission methods of OFDM technology and WIFI technology are currently the mainstream of UAV image transmission, and the more advanced technology is COFDM technology. In fact, in general, UAV long-distance transmission is actually a balance between distance and power consumption, which also involves many modulation techniques, such as spread spectrum to improve anti-interference ability, channel source technology optimization, and so on.