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GCN : May 2014
THE NEXT TIME a major hurricane or earthquake strikes, wiping out cell and wireless communications, first responders and citizens alike may be able to get gigabit-per-second wireless service from drones dis- patched to the skies over the a ected areas. DARPA s Mobile Hotspots program, just entering its second phase of development, aims to deliver secure, high-speed wireless networks to troops in remote locations, thus giving them fast and reliable ac- cess to intelligence and reconnaissance information. While DARPA s project is targeting military applica- tions, the same tech- nologies could be helpful during disas- ters and potentially for those conducting search-and-rescue operations in remote areas. The key to the program is deploy- ing millimeter-wave wire- less transceivers on small unmanned aerial vehicles (UAVs). And the challenge of doing that, of course, is engineering the components into footprints small and light enough for UAVs. Millimeter-wave communi- cations, which o ers band- width comparable to fiber optics, was actually first dem- onstrated in the 1890s. While Guglielmo Marconi was experimenting with radio waves at very low frequencies of 30-300 kHz. J.C. Bose first demonstrat- ed millimeter-wave transmis- sions in the extremely high- frequency range between 30 GHz and 300 GHz in 1897. It wasn t until the 1960s, however, that millimeter- wave technology was put to practical use by radio- astronomers. And it wasn t until the 1980s that millime- ter-wave integrated circuits were developed, enabling the use of those frequencies in commercial products. What makes millimeter- wave communications attractive is its e ciency and high throughput when used for point-to-point trans- missions. What makes it challenging, particularly for outdoor transmissions, is its susceptibility to loss of signal strength when transmissions go through rainfall and other atmo- spheric interference. In Phase 1 of the DARPA Mobile Hotspots program, participants -- and DARPA declined to name them -- fo- cused on refining and testing the underlying technolo- gies. According to a DARPA press release, the program success- fully demonstrated: • Smaller, steerable millimeter-wave antennas that can acquire and track a communications link between moving platforms. • Improved low- noise amplifiers that boost the communi- cations signal while minimizing unwanted noise. The prototype cut in half the noise levels of typical low- noise amplifiers, says DARPA. • More e cient and capable power amplifiers required to achieve the distances of more than 50 kilometers, as specified by the program requirements. • New approaches for robust airborne networking that allow maintenance of capac- ity between mobile air and ground units. • Initial engineering designs for low-size, weight and power (SWAP) designs for packaging the components. • Program requirements call for the final device to have a width no greater than 8 inch- es, a weight of less than 20 pounds and power consump- tion less than 150 watts. Phase 2 of the program launched in March 2014 with two participants --- L-3 Communications and FIRST RF --- designated to lead teams. The goal of Phase 2 is to integrate the technolo- gies demonstrated in Phase 1 into pods capable of being carried by a Shadow UAV. The Shadow, manufac- tured by AAI Corp., is al- ready extensively used by the military and is a medium- sized UAV that weighs in at 186 lbs. and has a wingspan of14feet. Itcanflyatupto 8,000 feet and has a range of 68 miles. DARPA has not made pub- lic when Phase 2 is expected to conclude. And neither L-3 Communications nor FIRST RF responded to requests for more information about the program s Phase 2 chal- lenges. It will, however, end with a ground demonstration of at least four pods capable of being carried by a Shadow UAV, two ground vehicles and a ground node. • UNMANNED AERIAL VEHICLES TO POWER WIRELESS HOTSPOTS -- ANYWHERE BY PATRICK MARSHALL EMERGING TECH 34 GCN MAY 2014 • GCN.COM DARPA.MIL DARPA'S Mobile Hotspots project aims to deliver secure, high-speed wireless networks to troops in remote locations.