Explained: US 5G issue and its implication for India’s carriers

By, Neha Tripathi, New Delhi
Jan 20, 2022 05:44 AM IST

The threat stems from the risk these airwaves pose to aircraft instruments, impacting at least some commonly used jets like the Boeing 777, which will need to undergo retrofitting to avoid the issue.

Air India announced it was cancelling some of its most popular direct flights to and from cities in the United States and some of the aviation sector’s biggest names globally have sounded alarm at the expansion of 5G mobile services in American cities.

US telecom majors AT&T and Verizon on Tuesday announced they were postponing activating 5G networks near airports for the time being.
US telecom majors AT&T and Verizon on Tuesday announced they were postponing activating 5G networks near airports for the time being.

The threat stems from the risk these airwaves pose to aircraft instruments, impacting at least some commonly used jets like the Boeing 777, which will need to undergo retrofitting to avoid the issue. The issue is unlikely to be a problem in Europe and Japan, where there have been enough changes in 5G deployment to ensure there is no interference, or in India , where the frequency band is different.

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The Directorate General of Civil Aviation in India said on Wednesday the issue is challenging for all stakeholders, and Boeing and Airbus last month warned that US operators alone could face revenue losses of up to $2 billion. US telecom majors AT&T and Verizon on Tuesday announced they were postponing activating 5G networks near airports for the time being.

HT takes a look at the issues involved, the implications for India’s carriers and the country’s own plans for the 5G upgrade.

Instrument interference risk

At the heart of the issue is the frequency at which the US telecom operators will run their 5G networks. AT&T and Verizon use the 3,700megahertz (mhz) and 3,980mhz frequencies in what is known as the C bband.

The concern of the aviation industry is that this frequency band is very close to the 4,200 MHz – 4,400 MHz (4.2GHz to 4.4GHz) frequency that aircraft use for equipment and communications -- particularly in a device known as radar altimeters. “5G interference could adversely affect the ability of aircraft to safely operate,” wrote Dave Calhoun, CEO of Boeing and Jeffrey Knittel, CEO of Airbus, in a joint letter to the US Transportation secretary Pete Buttigieg, in December.

Radio altimeters are critical for low-visibility landing, such as during spells of fog or heavy rain. They minimise the risk of accidents or collisions by accurate readings of the proximity to the ground.

Arun Kumar, director general of DGCA said: “It (rolling out of 5G communications in the US) is challenging for all concerned. We hope some amicable resolution takes shape sooner than later.”

Is India’s 5G plan also at risk?

Several telecom companies, Reliance Jio, Airtel and Vi, are expected roll out 5G services later in 2022. “In the post-pandemic world, connectivity is an important issue and a bigger asset for the economy. It is essential that the country has the required spectrum to meet the escalating demands for wireless connectivity as they will form an integral part of the growth of the nation,” said Lt Gen Dr SP Kochhar, director general, Cellular Operators Association of India (COAI).

At this time, India’s plans are unlikely to be affected because the band of radiowaves Indian telecom operators will use are further from the American C band, meaning there will be a large buffer to avoid interference.

“It has been decided by the government that spectrum in the frequency range 3,300-3,670 MHz should be made available to telecom service providers for international mobile telecommunications (IMT) and 5G,” said the Telecom Regulatory Authority of India (TRAI) in the latest consultation paper.

“In general, we believe this will be the starting point (mid-band spectrum) since it offers good 5G performance, though lower than high-band spectrum,” said Sriram Rupanagunta, co-founder and senior vice president of Aarna Networks, a company that has expertise in private 5G networks.

Rupanagunta added that several countries use 5G without such concerns and there are ways to address risks, such as by “reducing the power of the networks near the airports.”.

The Federation of Indian Pilots (FIP) and Air India did not immediately respond to requests for comment.

Reliance Jio, Airtel and Vi declined to comment, indicating that the COAI is the authorised body for dealing with these concerns.

Approach by other countries

The 5G implementation, including power levels of transmitters, frequencies, and proximity to flight operations have varied according to local guidelines, and there are differences with how more than 20 European Union countries have deployed 5G wireless transmitters near airports, compared with the US.

“Multiple countries around the world are deploying C-Band 5G in a way that has much less risk of interference with radar altimeters. The reasons include the fact that other countries are using reduced power-level limits or increasing the frequency spectrum spacing between 5G and radar altimeters,” said Captain Joseph DePete, president of the Air Line Pilots Association International (ALPA), in a statement.

Three main elements stand out. The transmitters (in Europe) have power capped at 613-watts, whereas rules in the US allow these to transmit at 1,585-watts—that’s two and a half times more. Second, transmitter deployment must give airports a buffer zone of 96 seconds of flight time, landing or take off. In the US, temporary guidelines factor in about 20 seconds as buffer.

“In France, the government required that antenna must be tilted downward to limit harmful interference. Similar restrictions do not apply to the US deployment,” the Federal Aviation Administration (FAA) has noted.

Similar guidelines for 5G networks in India, are yet to be finalised.

CTIA, or Cellular Telecommunications Industry Association, in its latest report points out that Japan has deployed 5G base stations up to 4100 MHz, with no interference with aviation services in the country. That means just a 100 MHz buffer zone.

“ ACMA considers that a 200 MHz guard band between WBB and radio altimeters is sufficient,” noted the Australian Communication and Media Authority in the latest guidelines for the use of the 3,700 MHz to 4,200 MHz band for 5G services.

Wide disruptions feared at present

According to FAA, there are 137 aircraft in the United States and 1,010 worldwide that still stand to be affected due to the risk of the frequency overlap, and will require either retrofitting or the use of alternative methods during low visibility landing.

An initial delay of the 5G roll-out, FAA said on January 3, allowed the aviation community and wireless companies to reduce the risk of delays and cancellations by getting more data, and identifying the nature of devices than can remain effective.

Since last week, FAA began issuing restrictions that airlines and other aircraft operators will face at many airports with the launch of new 5G wireless service. “Aircraft with untested altimeters or that need retrofitting or replacement will be unable to perform low-visibility landings where 5G is deployed,” the agency had said in a statement.

FAA, on January 16, cleared around 45% of the US commercial fleet to perform low-visibility landings at many of the airports where 5G C-band will be deployed. The agency also approved two radio altimeter models that are installed in a wide variety of Boeing and Airbus planes.

The airplane models approved include some Boeing 737, 747, 757, 767, MD-10/-11s and Airbus A310, A319, A320, A321, A330 and A350s.

Aviation safety expert Mohan Ranganathan said the situation was “definitely a threat to the aircraft but only when one uses any procedure or any equipment that involves the use of a radio altimeter”.

“However, CAT I (category I) on the instrument landing system (ILS) or LNAV (lateral navigation) and VNAV (vertical navigation) approach, which is satellite based and doesn’t use radio altimeter to determine height, is not affected,” he added. .

“By doing this (using these methods), they don’t have to cancel flights unless the weather conditions at the destination airport are bad. There is no need to panic,” Ranganathan said.

“Unfortunately, DGCA has not really implemented a procedure for LNAV and VNAV use in India, unlike other parts of the world, hence we do not have satellite based approaches,” he added.

The way forward: Frequency and equipment testing

The advantage that telecom players in India will have is the much wider buffer gap (around 530 MHz) between the highest range of the commercial C-Band for 5G and the lowest range of the C-Band used by aviation equipment. The other categories, which is low band 5G and mmWave networks, don’t at all interfere with aviation frequencies.

It is expected that India will likely open mmWave frequencies at a later time for 5G networks, but not in the first phase of the rollout.


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    Vishal Mathur is Technology Editor for Hindustan Times. When not making sense of technology, he often searches for an elusive analog space in a digital world.

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