On September 29, 2018, an unmanned aircraft was flying at Budapest Liszt Ferenc International Airport
Breakthrough in unmanned aerial vehicle positioning
We can say without exaggeration that Budapest Liszt Ferenc International Airport was the world premiere on the last weekend of September 2018. The experts of HungaroControl, headed by György Blazsovszky, telecommunication system development engineer, have proved that instead of GPS-based positioning of unmanned aerial vehicles it is possible - more secure - to have their mobile tracking. Until now, technology secrecy was in place with all partners involved in securing technology.
Thanks to Budapest Liszt Ferenc International Airport, Nokia, National Media and Communications Authority, Ministry of Defence, Rotors and Cams and HungaroControl for supporting the test.
The experiment has progressed in several ways, as it has already been challenging to issue a license to use the temporary airspace needed for testing at an operating airport. The mastermind, György Blazsovszky, told Radar that they had not previously been convinced that, in such a "radio interference" environment, unmanned aircraft would be able to fly at all. The Liszt Ferenc International Airport can also be considered an exciting location as the total number of impulses generated by radars and other devices in this area are of the order of megawatt, while unmanned aircraft respond to microwatts. When selecting a location, special care was taken to ensure that the experiment was conducted in a radio-interrupted environment. Testing has clearly shown that these conditions do not affect the control of remote control devices.
The time factor also did not favour the experiment: until mid-October, Nokia had to return the radio module that was used in the Budapest experiment, and the temporary airspace and frequency license were given for thirty days. György Blazsovszky has been involved in the implementation of the project and the related organizational tasks since May. “We actually had zero infrastructure, so thank you very much to Budapest Airport for the action and the media authority to provide free frequency. The excitement came out, and it was doubtful whether the test equipment would arrive in time, whether the software would be ready, and whether the owner BUD AP, the air traffic service provider HungaroControl and the Ministry of Defence would approve the temporary airspace request for this unmanned aircraft and operator for the mission, ”he said.
Finally, within three days, we were able to build a mobile network in the experimental area through which the positioning of the unmanned aerial vehicle was possible. That is, no positioning was made from GPS data. This is a huge step forward, because GPS-based navigation is not nearly as reliable, it can be disturbed by anyone, or even an error message is transmitted if it does not work properly. Nevertheless, the development and flight of unmanned aerial vehicles in the world is based on GPS, which, according to the engineer, is a serious problem. This is illustrated by the fact that if someone drives near a drone who uses an active GPS blocker, it is enough to confuse the orientation of an unmanned aircraft. That is why it is necessary to create at least a triple integrated system, which is determined by a mobile device with OTDOA function, an OTDOA provider (with adequate radio coverage), a flight plan, assisted GPS and other detection data.
Just such a technology was tested on the last weekend of September. It is important that authentication is based on a SIM card, and the engine of the system is LTE (Long Term Evolution, a fourth generation wireless data network) that communicates with codes, so it is difficult to disturb and collect data from multiple cell phones (up to 74) in parallel. The other great advantage of mobile positioning is that it replaces the installation of many thousands of euro on-board transponders. It is sufficient to place a LTE modem on the device, presence of a location service, so identification is provided by registering the device in the network. The only thing to do with ground control is to decide how often these data are retrieved.
The main advantages of the system are that it works without GPS, the on-board device can be operated with low weight, low power or battery operated, portable and can be used in small places. It does not require system integration on board non-autonomous aircraft. The on-board mobile device does not require regular calibration. The device has a unique identifier (IMEI - International Mobile Equipment Identity) with the Universal Subscriber Identity Module (USIM), which can be assigned to Mobile Station International Subscriber Directory Number (MSISDN). You do not need to set a transponder code for each flight. The system communicates the uncertainty and standard deviation of the measurement. It is easy to integrate into air traffic control systems (e.g. ASTERIX CAT20 format). For example, it may be possible to indicate on-board equipment if the GPS data is different from the OTDOA data and then display, upload and upload reliable, measured data. It opens the way for the safe operation of unmanned aerial vehicles, BVLOS (Beyond Visual Line of Sight), autonomous flights, Geo-exclusion and Geo-caging techniques. It also provides flights across borders or FIR (flight information region). Aircraft that are not currently "perceived" will also be visible and can thus be safely separated.
The drones are currently not bound to radio, so communication with them is impossible. However, the LTE modem or a data usage authorization (for research and backup and primarily for positioning) from the unmanned aircraft operator would solve this problem. "Practically, it is possible to track and isolate unmanned aerial vehicles, gliders, paragliders, airplanes, hot air balloons and ultralight aircraft with a mobile payment," he said. The only question is, since this positioning service is not yet available in Hungary, who will build it. There are several scenarios in this regard. According to one, HungaroControl would carry out the construction, the other said that the telecommunication companies operating in Hungary would make the investment, from whom the necessary service can be purchased.
In connection with this, György Blazsovszky also explained that the free use of the air space owned by the Hungarian state is a risk, and 60 percent of the air traffic is not visible to the management. There may be a right to pay for the use of the Drone-Zone in the future. However, this is missing from the draft legislation.
Mobile positioning is also used in emergency situations in North America, but it has not been the case in the air, in an integrated way, especially in airport conditions. The results confirm that the technology is absolutely viable: the system is based on only three activations of the possible 74 cells, based on latitude, longitude and 4 cells at different altitudes, for altitude measurements without any particular calibration, with an average accuracy of twenty meters. "It was clear to me on Friday at 11 am that this is working," he said.
György Blazsovszky himself is a private pilot and has spent over 16 years in mobile telecommunication research and development. The basic idea was the sum of these experiences, and the implementation was not helped by the network of contacts that enabled the Nokia company to participate in the project. At first, he would have been discouraged by the idea of saying that mobile phones would never play a role in flight. His bosses allowed him to deal with the project alongside his work, but only "if he didn't bother anyone". Finally, some 86 people took part in the testing. György Blazsovszky also obtained an airport license to transport people inside the airport.
According to the engineer, it is up to HungaroControl how this story continues, but I would not like to give up cooperation. "We are beyond the positioning, this is the first step, now we should achieve the use of mobile data connection to send air traffic control data for further processing on board equipment such as NOTAM, Weather, Flight Plan, vector coordinates (height, speed, direction), static and dynamic airspace and object coordinates (Geo-awareness), ”he pointed out. To do this, additional tests are needed to create a closed mobile network that provides at least nine cells and crosses national borders.
The expert is most pleased that he has proven to have a future in mobile technology in flight. However, operation and socialization of the system is still a big issue for the future.