AS INDIA’S telecom operators prepare for rollout of 5G services, the country’s aviation safety regulator has written to the telecom department flagging concerns over the likely interference of 5G C-Band spectrum with aircraft radio altimeters, The Indian Express has learnt.
A radio altimeter is an instrument that provides direct height-above-terrain information to various aircraft systems. The primary concern of the Directorate General of Civil Aviation (DGCA) emerges from the fact that these altimeters as well as a part of the 5G telecom services operate in the C-Band.
For telecom service providers, the C-Band presents a sweet spot for rolling out 5G services, ensuring coverage as well as high bandwidth, resulting in faster internet speeds. For aircraft operations, the use of altimeters in this band ensures highly precise measurements of the plane’s altitude.
“The DGCA is working in close coordination with the Department of Telecommunications (DoT) and has apprised it of its concerns over likely interference of 5G C-Band spectrum with aircraft radio altimeters,” said a senior government official.
These red flags are based on concerns raised by the US Federal Aviation Administration (FAA) over the last one year since telecom operators in the US, such as AT&T, Verizon and T-Mobile etc, began rolling out 5G services. In the US, an agreement between the FAA and the telecom operators resulted in a delay in rollout of 5G services in the C-Band near airports that were assessed to be difficult for pilots to make visual approaches.
“The radio altimeters pick up the faintest signals reflected off the ground in the assigned frequencies to achieve highly accurate results. This makes it possible for the instruments to pick up what are known as ‘out-of-band’ signals. These out-of-band signals could significantly impair functions of a radio altimeter,” said another official.
A third official at the DoT, however, played down the impact. “We have auctioned C-Band spectrum in the frequency ranging from 3.3 GHz to 3.6 GHz (in India). Aircraft radio altimeters mainly use frequencies ranging from 4.2-4.4 GHz. So, there is a significant 500 MHz gap between the two frequency ranges. Having said that, the telecom department has taken note of the concerns flagged by DGCA, and we are working together,” said the official.
The official said the issue in the US became significant because operators there are deploying 5G services in the 3.7-3.98 GHz frequencies, which is closer to the radio altimeter frequencies.
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The DGCA and DoT did not respond to e-mails sent by The Indian Express, seeking their comments.
Earlier this year, Air India had to cancel some of its flights to the US as airlines globally scrambled to reschedule flights amid concerns that the rollout of 5G mobile services in the US could potentially interfere with aircraft navigation systems. Even at the time, the DGCA had coordinated with Indian carriers on the issue.
Over the last year, the FAA has issued several directives to airlines to install certain filters or modify their equipment to ensure that 5G airwaves do not interfere with their navigation systems.