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drones Drones’ agenda: new spectrum By Junko Yoshida As the term UAV (unmanned aerial vehicle) suggests, drones are supposed to fly autonomously. And there’s the rub. Unresolved questions for regulators and drone manufacturers are: a) how drones, while flying, can maintain a reliable communication link with the ground for “command and control,” and b) if so, what communication spectrum is available. Panelists on the recent EE Times’ Radio Show on drone talk debated what lies ahead for commercial drones. As currently proposed rules for commercial drones are written (proposed in Feb. by FAA), drones are banned from flying at night and operating beyond line-of-sight. More important, under proposed rules, “drones can’t fly over personnel unrelated to a drone project,” noted lobbyist Michael Drobac, executive director of the Small UAV Coalition, during the radio show. In essence, “you are for the most part prohibiting the use of drones for commercial purposes all together,” stressed Drobac. The irony of the proposed drone regulation is that it permits “no robotization.” “It’s as if we are putting some sort of manned overlay over what’s supposed to be an unmanned system,” Drobac summed up. The chief concern that emerged during the drone debate is the communication link between drone and pilot. The key Michael Drobac question is whether drones need a dedicated communication spectrum, or if Wi-Fi and cellular communication links suffice. 5GHz for dedicated drone communication The drone industry will be getting two bands they can use for dedicated communication. The World Radio Conference, which takes place every four years, has already approved — in 2012 — “a spectrum around 5GHz” for command and control of UAVs, explained Jim Williams, ex-FAA chief. This is a vacant band originally set aside for “microwave landing systems.” It’s designed as an all-weather, precision landing system for aircraft. This spectrum has since been made obsolete by the wide availability of GPS, he said. Hence, it’s unused. There is also “a small chunk of L-band around 1GHz” – originally set aside for aircraft to see ships at sea, now approved for dedicated drone communication, he added. During the radio show, Williams acknowledged that a handful drones today are permitted to fly in the United States beyond line of sight and over people. But one of the requirements is that they have “reliable communication between a pilot and an aircraft.” Those drones with permission to fly beyond line of sight, for example, depend on relatively unregulated public frequencies used by Wi-Fi and mobile phones. Williams noted, “But those frequencies are set up in such a way that is not tremendously reliable, since when a lot of people are using it, your range drops.” In some incidents, drones flew away when signals got jammed, he added. Although drones are getting smarter and are dealing with such potential problems, Williams insisted, “Reliable communication is a key for the drone industry.” For that, the world is moving toward allowing drones to use a dedicated spectrum – within 5GHz – for their communications. Asked about the reliability of Wi-Fi and cellular networks as communication links, Yannick Levy, vice president, corporate business development at Parrot, said, “As a drone maker, I’d like to say that both Wi-Fi and cellular networks are good networks, developed by professionals. They have redundancy in place.” But he acknowledged that The French Civil Aviation Authority (Direction générale de l’aviation civile, DGAC) doesn’t allow commercial drones to use cellular networks, either. “They want a special network dedicated Yannick Levy to drone flight.” What about Delair-Tech, the French drone company known as the first civilian UAV in the world approved by an official government agency to fly beyond visual line-of-sight? Delair-Tech’s drones use 3G for communication. Levy said Delair-Tech is one of the French drone companies allowed to fly beyond visual line of sight, with their drones having a cellular modem on-board. “Their intent is trying to demonstrate that it works.” Who will manage the spectrum? Although the FCC recently changed the U.S. table of allocation – issuing rules about what can and can’t be done to various portions of spectrum, drones can’t yet begin to transmit signals on those bands. According to Williams, “channelization schemes” need to be worked out, which are essentially rules about how much power you can transmit, what centre frequency you have to use and what out-of-band power you can tolerate, etc. The Radio Technical Commission for Aeronautics (RTCA) is working to establish such rules. They’re due next summer. The regulatory process Jim Williams 20 Electronic Engineering Times Europe September 2015 www.electronics-eetimes.com


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