Video streaming by IEEE802.11p
In China alone, there were more than 400 drone companies in 2015. In this fast-growing market, it is important for drones to differentiate themselves. To differentiate, DJI has developed a video transmission system Lightbridge that has led to the success of its Phantom series.
[2.1] Current technologies for video streaming
We can classify current technologies in the following four categories:
Analog video transmission – Analog video transmission systems have bigger size and consume more power to reach the same distance compared with digital. Another weakness is its poor resistance to interference. Therefore, analog has been replaced by digital systems in most products. However, its low latency characteristic still makes it popular among drone racers who want real time video displays with zero latency.
Wi-Fi – After analog systems, Wi-Fi has become the most popular solution. It provides enough data throughput and is offered at a very low price. Nevertheless, Wi-Fi can only reach a few hundred meters under clear channel with line-of-sight communication. Since most Wi-Fi devices are working in 2.4 GHz ISM band, which is probably the most crowded band worldwide, the communication range normally drops to less than 100 meters. Other drawbacks include high latency and long reconnection time in cases of signal loss.
Proprietary solution – To overcome the drawbacks of Wi-Fi, some drone companies have developed proprietary solutions. The Lightbridge from DJI is the most well-known. The newly announced Lightbridge claims to reach 4km (CE power regulation) with good results on communication latency and reconnection speed. However, proprietary solutions also mean high costs. Companies must absorb all development cost themselves.
Cellular – Intel and AT&T started testing drones with LTE embedded. Convenience is the selling point, since video is directly uploaded to the cloud, but it is certainly not a mainstream solution. The first issue is the cost as LTE modems are relatively expensive. The recurring cost for using LTE network are also a hurdle. Other drawbacks include high latency and limited flying areas due to LTE network coverage.