Air traffic disruptions in the USA due to 5G and Radar Altimeter interference issues can be attributed to the introduction of 5G service by AT&T and Verizon in frequency bands not identified by the International Telecommunication Union (ITU) for IMT (International Mobile Telecommunication) or 5G.
These two major service providers in the US paid US$80 billion during FCC (Federal Communication Commission) auction of C-band frequency range 3700 to 3980 MHz in early 2021 for the operation of 5G service. This range sits outside the band 3300 to 3700 MHz that was identified by the ITU for 5G/IMT during its World Radio Conference in 2015 (WRC-15),
Radar Altimeters provide critical support to aircrafts while landing, specially under low visibility conditions and have been operating globally since 1970 in 4200 to 4400 MHz band. This Altimeter band now sits closer to the frequency band auctioned for 5G in the USA and has the potential to receive harmful interference in both passenger and cargo aircrafts.
The aviation industry and the Federal Aviation Administration (FAA) have been flagging this issue with FCC since 2018 on the need to ensure that Radar Altimeters be protected from 5G interference.
Every administration can exercise its sovereign right to choose what is best and what provides better economic benefits for the country. In this case, however, the USA, as one of the 193 members of the ITU, has obligations towards ITU’s Radio Regulations and any departure from ITU’s Radio Regulations loses the benefits of international compatibility and harmonization of radio spectrum use and could lead to unforeseen harmful interference to vital communication links or networks.
This departure in the present case has caused heavy disruption of air traffic in the United States and also affected foreign carriers to fly in and out of the USA.
ITU, a Specialized Agency of the United Nations, allocates radio spectrum to 41 radio services after a detailed compatibility analysis during its four-year study cycle, to ensure the protection of incumbent services besides global harmonization of frequency use.
ITU’s Radio Regulations, an international binding Treaty document, was first put together in 1906 and subsequent ITU Conferences have revised these Radio Regulations 39 times to accommodate radio spectrum requirements for new technologies and growing requirements of existing services, with one primary aim – wireless communication must be interference-free. While making allocations for new services by WRCs, one of the cardinal principles is that the existing services should not be unduly constrained.
Globally harmonized use of radio frequencies, as contained in ITU’s Radio Regulations, is in everyone’s interest and that includes the airline industry and equipment vendors. Deviation in this regard can have serious implications as is evident from the 5G case in the USA.
Even the vendors and operators of 5G/IMT equipment, through their 3GPP (3rd Generation Partnership Project) group, have been asking for harmonized spectrum, though mainly for achieving economies of scale.
Spectrum for 5G auctioned and deployed by FCC in USA, is part of the frequency band n77 of the 3rd Generation Partnership Project (3GPP) - release15. Evidently this 3GPP band has not undergone detailed compatibility studies and consultation process as done under the auspices of ITU.
ITU’s next World Radio Conference in 2023 (WRC-23) allocation to IMT / 5G with suitable measures/conditions could provide improved compatibility with Radar Altimeters. It proposes to consider among other bands, 3600 – 3800 MHz, for IMT / 5G. Whether this band would be ultimately identified for IMT by the WRC-23 would depend on the current compatibility studies being undertaken by the ITU and the WRC-23 deliberations.
Mitigation measures undertaken by the FCC & FAA in consultation with 5G operators in USA to keep the avionics up and running both for passenger and cargo movement may only be termed as short term.
It may be unlikely that in view of the high price paid for the 5G C-band spectrum in US, any new attempt to conform to ITU’s Radio Regulations would be made and one would need to await the results of ITU’s World Radiocommunication Conference in 2023.
While Japan and South Korea, both operate their C-band 5G/IMT networks closer to the Radar Altimeter frequency band even as compared to USA, there are no reliable reports of any harmful interference with Radar Altimeters because these countries operate IMT/5G at a fraction of the power levels permitted in the United States.
Reduction in power levels and other interference mitigation measures have been resorted to by countries that have chosen to use frequency bands for IMT / 5G not identified by the ITU. Even FCC, USA is now learnt to have asked its 5G operators to use much lesser power near the airports, so that the operation of Radar Altimeters, especially during landing in bad weather, is not impacted.
Considering the importance of ITU and its Radio Regulations to India, the Indian administration decided to be one of the highest contributors to the ITU Budget. It pays 10 Contributory Units/year to ITU that is equal to about 3.3 million Swiss Francs/year (Indian Rs 27 Crore per annum). The developed economies of the USA and Japan, which are the two largest contributors to the ITU, contribute 30 Units each i.e. just three times the Indian contribution. India also has the governmental setup called Wireless Planning & Coordination (WPC) Wing under Ministry of Communications to ensure adherence with ITU’s Radio Regulations.
India has chosen to go in for auction of the band 3300 – 3670 MHz that is not identified by ITU for IMT in India beyond 3600 MHz. The identification is only for the band 3300 to 3600 MHz.
The C band (3700 – 4200 MHz) is also globally deployed for Fixed Satellite Service (FSS) as per ITU’s Radio Regulations. This use does not cause any interference to the adjacent band 4200 – 4400 MHz used by Radar Altimeters because the signal strength that reaches the Earth from the Geostationary satellite located 36000 kms. away, is extremely low.
It cannot be emphasized enough that conformity of national frequency use with ITU’s 'Radio Regulations’, an internationally ratified binding treaty document, leads towards an interference free operation of various wireless services due to meticulous and time-tested procedures & study methods that aim to ensure interference free coexistence of various radio services.
Departure by any administration from the frequency allocation table of ITU’s Radio Regulations can have serious international ramifications in the absence of detailed technical studies. It is incumbent on ITU member administrations to fulfill their obligations towards the binding international treaty called ITU’s Radio Regulations.
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