Inside Unmanned Systems

APR-MAY 2017

Inside Unmanned Systems provides actionable business intelligence to decision-makers and influencers operating within the global UAS community. Features include analysis of key technologies, policy/regulatory developments and new product design.

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12 unmanned systems inside   April/May 2017 air traffic systems are compatible with ADS-B. It also fits well with law enforcement because enforcers can either directly receive ADS-B broadcasts via inexpensive receivers or sim- ply see ADS-B traffic via the internet. Finally, ADS-B helps tremendously with DAA. Even if a drone goes "lost link," it could still avoid ADS-B compliant traffic using its on-board receiver. The problem with ADS-B is spectrum band- width saturation. Although the FAA hasn't yet conducted extensive research on the subject, in theory, several hundred drones all broadcast- ing on ADS-B in the same area could overload the system. I think the FAA should research this theory thoroughly before saying "no" to ADS-B. For example, they should see if reduc- ing the broadcast power on ADS-B Out from 50 watts to something more appropriate for small drones, like 5 watts, solves the problem. They should see if reducing the polling rate for drone ADS-B Out reduces saturation by not constan- tantly broadcasting their position. Both efforts could substantially reduce saturation. LTE: This is my favorite. I don't score it as high as ADS-B for safety because LTE isn't aviation-standard equipment nor does it op- erate on aviation-protected spectrum, so in- terference is a potential problem. LTE secu- rity is better than ADS-B because cell phone companies have decades of experience with cellular security and LTE can easily use certifi- cate or SIM card-based ID. LTE also doesn't currently directly interface with air traffic control systems like ADS-B does. There are, however, work arounds to these problems. NASA's Unmanned Traffic System (UTM) embraces Internet connectivity as a core function. Unlike manned aircraft that must rely solely on RF-based systems to exchange information, remote pilots and unmanned traffic managers can use Internet connectiv- ity to relay and receive track data from both ADS-B and LTE connected drones. UTM can easily rebroadcast select drone LTE tracks via TIS-B to ADS-B In equipped aircraft if algo- rithms decide drones get too close to manned aircraft, or to each other. LTE works well for law enforcement because they can either inter- rogate LTE drones directly or use an internet solution for tracking. LTE works well for DAA as long at the unmanned aerial system (UAS) maintains LTE connectivity to receive tracks from UTM. The problem with LTE is that a drone that loses its LTE link is blind and can't see traffic around it, whereas an ADS-B drone could perform DAA autonomously even with- out a command link. An LTE only solution also puts low f lying manned aircraft (primar- ily general aviation aircraft and particularly helicopters) at much greater risk because they f ly with ADS-B only and don't have LTE con- nectivity to see drone traffic. RADIO: The "probably not a good idea" zone starts with RF beacons. Making an RF beacon is dead easy. All you need is a GPS feed and a broadcast frequency. And there's the prob- lem—where do we find uncongested, available RF spectrum these days? It's not a problem in some countries; the United Arab Emirates has long protected spectrum for falconry bea- cons and will use them for their drones. It's a BIG problem in the U.S. Add to that all the drawbacks of using non-standard aviation equipment and safety concerns with unpro- tected spectrum and you end up asking why you'd want an RF beacon when either ADS-B or LTE accomplish the same job with widely used equipment operating in better protected spectrum. WiFi: This goes further into the "not a good idea" zone. True, WiFi equipment is ubiqui- tous and spectrum is available, but it's VERY I'LL HAVE TO ADMIT, ADS-B IS MY FAVORITE SOLUTION. IT'S THE SAFEST BECAUSE 'ADS-B OUT', WHICH BROADCASTS AN AIRCRAFT'S GPS POSITION CONSTANTLY, IS ALREADY MANDATORY EQUIPMENT FOR MANNED AIRCRAFT BY 2020. General Overview by James Poss, Maj Gen (RET) USAF

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