To communicate with a drone from a smartphone, the most widely used solution today is a telemetry dongle at different frequency bands depending on the country you are located in (433MHz, 868MHz or 915Mhz). This however requires to have an additional piece of hardware connected on the smartphone. This is why we have investigated an other solution to have a direct connection with the drone without additionnal piece of hardware: Bluetooth.
We have been implementing Bluetooth connection since end October and testing it on our various prototypes – and guess what ? it works ! I would say it flies ! Basically we now have a Bluetooth module on the HEXO+ drone communicating with the smartphone. We have been testing it at low speed, high speed (up to 70km/h), in line of sight, in pockets, or even in a car and we have good results: HEXO+ keep the connection with the smartphone in all cases tested and follows and frames you. The videos you might have seen from CES Las Vegas in a buggy covered by the BBC and in a BMW car, covered by the Verge are based on this Bluetooth system and you can see the results. We never had issues for the past 2 months for distance below 60 meters when the drone is in the air, which is good enough to get great video shots of you in actions. We have even reached 100m in some cases.
The only issues we have faced so far and that we are further investigating is when the drone is on the ground. We don’t have a good connection between the Bluetooth antenna and the smartphone depending on where you stand (especially in a car at 20m from the drone) due to the fact that the bluetooth antenna is under the drone and thus doesn’t have a line of sight view with the smartphone. Those are cases we are evaluating to see how we can improve the system by fine tuning antennas positions on the drone, and looking at software solution to handle those cases. We are also looking at developing features to handle HEXO+ behaviour depending on the link quality.
We will nevertheless go through a more thorough testings to understand the limits of performances – we are thus developping a specific function in the smartphone app so that we would be able to share details about round trip time and throughput we can achieve at different ranges. For those of you who want to know more, we are using Bluetooth class 1 module at 2.4GHz, with receiver sensitivity better than -90 dBm, output power of 19 dBm, weighting less than 4 g and consuming less than 100 mA, with omnidirectional antenna. On the smartphone, we have been testing it mainly with android platforms: Samsung Galaxy S4 and S5, Sony Ericsson Xperia E3, Motorola G 4G, and Wiko Darkmoon.
There are advantages in using Bluetooth: first, it is easier from end user experience perspective: you don’t need to add anything on your smartphone – no dongles, no additional hardware. Second, we observe less interference on the drone itself which translate in better reliability (less noise on the electronics components). Next step is to test it on iOS: stay tuned !