Operations Center (Chicago)
The letter from the new US Transportation Secretary, Pete Buttigieg, to the 5G operators is polite but clear: there are difficulties with the 5G network, which operates in the GHz range and could interfere with weaker positioning signals in the vicinity of airports. 5G was supposed to launch on January 5th.
The planned rollout by US operators Verizon and AT&T had already been delayed because interference with weaker—but crucial for commercial jet approaches—geoposition signals in the airport vicinity could not be ruled out with sufficient certainty. On December 31, Buttigieg thanked CEOs John T. Stankey and Hans Vestberg for the "ongoing dialogue" and their understanding regarding the already incurred one-month delay. "We are working to find a solution," Buttigieg said, "that will create confidence that 5G C-band and aviation are safe and United States can coexist The Department of Transportation acknowledges the significant investments by both companies to date , as well as the importance of expanding 5G service for the economy. Nevertheless, serious problems are feared, particularly in poor visibility and during automated landing approaches. "This would lead to unacceptable disruptions" - because where conflicts occur, flights might even have to be rerouted or destinations cancelled.
Steve Dickson (FAA)
Asa short-term solution to enable the coexistence of 5G deployment in the safe flight operations ensure , US authorities and the Federal Aviation Administration under the leadership of beyond January 5th wait two weeks. Buffer zones are to be established around the airports to avoid conflicts on the frequency band. "Our goal would then be," says Buttigieg, "to determine attenuations (in the transmission power of installed cell towers and relay masts) for all priority airports that will allow most large commercial aircraft to operate safely under all conditions." Concerns about the 5G and C-band occupancy have also been raised by aircraft manufacturers Boeing and Airbus. anticipates The US Department of Transportation activating . the C-band sites on a rolling basis, but not until the end of MarchThe main issue appears to be the compatibility of the frequencies used for radio-controlled altitude measurement. The FAA reportedly wants to reach an agreement with the operators on "alternative methods" at the airports in question.
Fig.: FAA
Radio measurement specialists like Rohde & Schwarz pointed out some time ago that while 5G a offers is already being used for satellite downlinks to satellite earth stations (SES).
The C-band allows coverage of entire continental zones and is allocated to fixed-line satellite communications. In the US, the frequencies from 3.7 GHz to 4.2 GHz are designated for downlink, and in Europe, from 3.4 GHz to 4.2 GHz. Radio engineers say the C-band is sparse or nonexistent is. Another advantage of the C-band is its low susceptibility to rain, which allows for stable connections in tropical regions. "Furthermore," Rhode & Schwarz adds, "C-band services play a crucial role in emergencies and disaster scenarios." Sharing a frequency spectrum with other parties can disrupt existing services. "In the downlink, low-noise signal converters (so-called "repeaters" or radio relay stations) can enter a saturation state due to interference."
Frequency band measurement technology (Rhode & Schwarz)
Frequency filters are ineffective in addressing this problem. A position signal that over several thousand kilometers from the geostationary orbit of a satellite used for this purpose to Earth isno is already weak and might then become undetectable. While legal limits provide a general guideline for the planning of mobile networks, compliance with these limits by means guarantees that interference will not propagate further than predicted in individual cases.
Wireless technology providers recommend testing with so-called "vector signal generators" to assess reliability in 5G environments and prevent potential interference from alternative technologies. The time required to conduct and verify such tests in each individual case is a crucial factor.
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