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1 1 (January 26, 2022)

handle is hein.crs/govefei0001 and id is 1 raw text is: C o g e s o a R es arc S e v January 26, 2022 Aviation Concerns Regarding the Rollout of 5G Wireless Telecommunications Networks The rollout of fifth-generation (5G) wireless telecommunications networks in the United States has roiled passenger and cargo airlines and other aviation operators over fears that certain mid-band or C-band 5G signals could interfere with aircraft radio altimeters. These concerns prompted the Federal Aviation Administration (FAA) to issue alerts to aircraft operators in late 2021 about possible flight safety risks. FAA asked aircraft operators for related data, urged them to educate pilots about potential disruptions, and prohibited certain flight procedures as a safety precaution. At the urging of FAA, the Department of Transportation, the White House, and some Members of Congress, telecommunications companies agreed to voluntarily delay the rollout of 5G service near airports, originally scheduled for early December 2021, until July 2022, to avoid air travel disruptions. This will give FAA and avionics equipment manufacturers additional time to more thoroughly assess whether C-band 5G signals might interfere with flight operations and whether equipment upgrades or other mitigation actions will be needed to adequately shield aircraft systems from 5G interference. Radiofrequency Spectrum and 5G Signals 5G networks are being installed all around the world, but are being assigned different frequency bands in different countries. While low-band (below 1 gigahertz (GHz)) and high-band (above 24 GHz) 5G frequencies pose no particular concern to aviation, the assignment of C-band frequencies in the range of roughly 3 to 5 GHz has alarmed the aviation industry over potential interference with radio altimeters. Europe has allocated spectrum between 3.4 and 3.8 GHz for C-band 5G, while in Japan, frequencies from 3.4 to 4.1 GHz are assigned. In the United States, the Federal Communications Commission (FCC) approved use of spectrum between 3.7 and 3.98 GHz for 5G in 2020, and subsequently auctioned licenses in this band to telecommunications providers. U.S. providers paid over $81 billion for C-band licenses, and are eager to launch service in order to recoup these costs and realize a return on investment in 5G technology that will give wireless customers faster data transmission speeds and greater reliability than fourth-generation (4G) wireless service. Potential interference with Radio Altimeters Worldwide, aviation operators have long used a slice of radiofrequency spectrum between 4.2 GHz and 4.4 GHz that is exclusively reserved for radio altimeters. These devices, frequently installed on airliners, regional and business jets, turboprops, advanced helicopters, and military aircraft measure aircraft altitude above the ground by timing how long it takes for a directional radio transmission to reach the terrain below and bounce back to an onboard receiver. Radar altimeters provide input to aircraft terrain alerting systems that provide pilots with information and warnings about terrain and obstacle clearance. Radar altimeters also provide data to automated flight control systems used for vertical flight guidance at low altitude, especially during approach to landing. While airplanes can rely on other systems, including precision instrument landing systems, to descend to about 200 feet above the ground, radar altimeters are essential to providing vertical guidance below 200 feet in low-visibility conditions when pilots are unable to clearly see the runway. While such capabilities are essential for all-weather commercial flight operations, radar altimeters are not commonly found on small general aviation aircraft. FAA, along with aviation regulators from other countries, first raised concerns about wireless deployments in the C- band in 2015. They cautioned that 5G signals transmitted on nearby frequencies could potentially interfere with radio altimeters, particularly if high-powered 5G base stations are placed close to airport runways. Although not required by regulation, most radio altimeters currently in use have mask filters to block signals on nearby frequencies that could be mistaken for reflected radio altimeter signals. However, it is uncertain whether these filters will adequately block more powerful 5G signals in all cases, as radio altimeter signals. A study by RTCA, an aviation industry technical advisory group founded as the Radio Technical Commission for Aeronautics, concluded that expected interference levels from fundamental 5G emissions in the 3.7-3.98 GHz range and spurious or stray 5G emissions that bleed over into the 4.2-4.4 GHz band were likely to exceed safe interference limits for all envisioned 5G transmitter configurations across all categories of airplanes and helicopters equipped with radio altimeters. Moreover, it determined that stray 5G emissions that might bleed over into the band reserved for radio altimeters would not be considered compliant with international recommendations for radiofrequency protection criteria. The FCC countered that the RTCA findings assume a worse-case scenario, and that alternative testing found that FCC-mandated protections, including limits on the strength of 5G signals and 220 MHz of spectral separation between 5G signals and radio altimeters, would mitigate the potential for interference. Further, the FCC argued that properly engineered radio equipment should not be prone to harmful interference from 5G signals. Near-Term Mitigation Actions Telecommunications providers voluntarily pushed back 5G launch schedules from early December 2021 to January 2022 to provide FAA with additional time to address radio ittps://Crsreports.congress.g( 0

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