Multi-rotor aircrafts use wireless technology to transmit the images captured to ground devices, pilots can view the video in real time. To provide environment information and camera views in time, video transmission requires low latency, long transmission range and excellent anti-interference ability.
Video transmission is realized by either digital signal or analog signal. Usually drones without gimbal cameras apply analog signal. Despite that video rarely gets stuck or loses frame with analog signal, it is highly power-consuming. With transmission range being 2km, the transmitted power goes far beyond what is allowed by authority. Moreover, video streamed back is in standard definition, which is unsatisfying.
Three major video transmission technologies using digital signal are: DJI Lightbridge, OcuSync and Wi-Fi. DJI Lightbridge and OcuSync are DJI’s patent communication link technologies. With transmission range of 7km and ability to stream video as clear as 1080P, DJI Lightbridge and OcuSync outpace Wi-Fi video transmission greatly.
DJI Lightbridge
Fast Communication Link
Wi-Fi uses traditional protocol stack, so a handshake mechanism must be established between transmit end and receive end first. It takes several seconds to ten seconds to establish or re-establish the communication link (when step-out happens), leading to latency in communication. The communication in DJI Lightbridge is directly linked between physical layers, so the communication link is fast and prompt without protocols.
Long Transmission Range and Ultra-clear Image
Lightbridge is able to transmit 1080P video. With optimized compression algorithm, video can be streamed fluently on complex channels. Advanced codec algorithm and improved frame structure ensures demodulation process even with weak signals. Meanwhile, the RF circuit is optimized to receive weak signals without being greatly interfered by noises.
High Reliability
DJI Lightbridge 2 applies a wireless HD image transmission technology, which dynamically weighs transmission distance, electrical environment and image quality for best effect. In addition, Lightbridge 2 would automatically choose the best channel, switch to a better channel or adjust the band width of video when necessary. In this way, the occasion of losing frames and video stuck could be avoided as possible, increasing the reliability of wireless video transmission.
Multiple devices
Lightbridge supports multiple controllers to control one aircraft at one time. In a typical scenario, pilot would use master controller to command the flight, while gimbal operator uses the slave controller to adjust gimbal to finish complex shooting task. With multiple controllers connected, each of them could send order to aircraft via master controller, or receive video and flight data from aircraft via master controller.
2.4/5.8GHz Control Frequencies
Selectable 2.4GHz and 5.8GHz frequencies are supported by the Inspire 2. Generally speaking, a 2.4GHz Wi-Fi video transmission system is used with a 5.8GHz remote control link providing aircraft control. This is because if the video transmission and the remote control links use the same frequency, interference between the two may cause signal loss. This same rationale is why interference may be caused by other users of radio frequencies in surrounding areas. The Inspire 2’s new Lightbridge HD video transmission system uses a Time-division multiplexing mechanism to transmit both video feed and remote control signals on the same frequency. In urban areas, the 2.4GHz frequency band may suffer from high levels of signal interference from sources such as Wi-Fi routers and 4G base stations. As an option, the 5.8GHz frequency provides a broader communication bandwidth and has more available channels for transmission, making it more suitable for stable signal transmission in these types of environments. After powering on, the Inspire 2 automatically scans the environment and selects the band with the least amount of interference, ensuring optimum video feed quality and remote control reliability.
OcuSync
The Mavic uses DJI’s newly developed OcuSync transmission system. Part of the Lightbridge family, OcuSync performs far better than Wi-Fi transmission at all transmission speeds. OcuSync also uses more effective digital compression and channel transmission technologies, allowing it to transmit HD video reliably even in environments with strong radio interference.
Excellent Video Quality
Compared to traditional analog transmission, OcuSync can transmit video at 720p and 1080p – equivalent to a 4-10 times better quality, without a color cast, static interference, flickering or other problems associated with analog transmission. Even when using the same amount of radio transmission power, OcuSync transmits further than analog at 4.1mi (7km)*.
Stable Communication
OcuSync goes even further than optimizing the communication mechanism and parameters of aerial imaging. There are several video transmission systems on the market claiming to offer video transmission with zero latency. However, it should be noted that the physical layer of those transmission systems is too simple to adapt to changes in the environment. When affected by signal interference, the image quality of the video being transmitted will fall sharply. This means these systems are not suitable for far field transmissions and transmissions in interference-heavy environments.
Also, because these video transmission systems are not integrated into the whole system, latency will immediately start to rise up from 0 when working with devices including cameras and displays. OcuSync is able to strike a perfect balance between latency and receptivity, reducing latency to 5ms for remote controller transmission commands, 10ms for video data and 130ms for videos. More than low enough to ensure that Mavic is able to fly reliably despite interference. OcuSync’s integration with video processing, coding, and signal transmission systems also make it more cost effective. Before taking off, OcuSync will automatically scan the environment and choose the frequency band with the lowest interference, ensuring more stable video transmission.
Fast Communication Link
As Wi-Fi was primarily designed to connect electronic devices locally, it works best when connecting to nearby devices. As it was designed for short range, Wi-Fi systems use low cost transmitters that suffer from weak data links. This means that a Wi-Fi cannot detect weak signals or signals with interference. OcuSync however, uses many cutting-edge communication industry technologies to outperform Wi-Fi in terms of sensitivity, anti-interference, and anti-fading, as well as when flying at high speed. It also supports simultaneous connection to multiple devices.
Multiple Devices
As well as point-to-point video transmission, OcuSync also supports wireless connections to multiple devices. For example, you can connect the DJI Goggles, remote controller, and Mavic wirelessly to OcuSync all at the same time. You can also add an additional remote so that you can control the Mavic with two remotes or share First Person View (FPV) videos.
* Unobstructed, free of interference, when FCC compliant.
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