The Federal Aviation Administration (FAA) started issuing hundreds of notices related to the rollout of C-band while it continues to determine which radar altimeters will be reliable and accurate when 5G C-band gets deployed in the U.S.
AT&T and Verizon are expected to launch their C-band spectrum in support of 5G services starting Wednesday, January 19, after twice delaying due to aviation concerns. The spectrum at 3.7 GHz is close enough to radio altimeters at 4.2-4.4 GHz to cause concern at the FAA, although the FCC determined a 220 MHz guard band is sufficient protection.
The FAA said aircraft with untested altimeters or that need retrofitting or replacement won’t be allowed to perform low-visibility landings where 5G is deployed, pointing to the Notices to Air Missions (NOTAMs) that it started publishing on Thursday. The NOTAMs specify information on restrictions or procedures that pilots and others need to follow.
To size up the FAA’s concerns: More than 1,300 NOTAMs were expected to go out in what Bloomberg described as one of the most sweeping set of NOTAMs in the FAA’s history.
Guidance included in the NOTAMs could range from simple advisories about 5G network operations in the area to prohibitions of some instrument approach procedures due to potential interference affecting radar altimeters, noted the National Business Aviation Association (NBAA).
Still a lot up in the air
The FAA said that with additional transmitter location data, it was able to determine that in the initial deployment of 5G C-band, aircraft will be able to safely land in low-visibility conditions on some runways without restrictions. But it doesn’t know if that will be possible in subsequent 5G C-band deployments.
“Since the agreement with the wireless companies was reached, the agency has made progress to safely reduce the risk of delays and cancellations as wireless companies share more data and manufacturer altimeter testing results arrive,” the FAA said in a statement Wednesday.
The agency said it expects to provide updates “soon” about the estimated percentage of commercial aircraft equipped with altimeters that can operate reliably and accurately in the 5G C-Band environment.
Radio altimeters provide information about an aircraft’s height above the ground and the data they provide informs other safety equipment on a plane, such as navigation instruments and collision-avoidance systems, according to the FAA.
Clashes and negotiations over C-band deployments were fully underway leading up to the recent New Year’s holiday. In the end, AT&T and Verizon agreed to delay their 3.7 GHz C-band deployments until January 19 after U.S. Secretary of Transportation Pete Buttigieg asked for more time. Part of the FAA’s job during the extension was to issue the NOTAMs and begin a process of clearing altimeters shown to be reliable and accurate alongside 5G.
The wireless carriers also agreed to provide buffer zones around 50 airports to reduce the risk of interference, turning off transmitters and making other adjustments. Wireless carriers publicly have downplayed the significance of these zones for their own services, saying they can still use their millimeter wave and other spectrum to provide 5G.
However, AT&T and Verizon are eager to put their C-band to use in other parts of the country after spending the lion’s share of the $81.2 billion raised in the C-band spectrum auction last year. Verizon was the biggest spender, at over $45 billion, while AT&T committed more than $23 billion for C-band spectrum.
Earlier this month, Verizon said it will cover more than 100 million people when it turns on its C-band spectrum for commercial use, providing speeds up to 10 times faster than LTE. While it’s already offering high-speed 5G under the “Ultra Wideband” label using millimeter wave spectrum in pockets of cities, the mid-band C-band spectrum provides both super-fast speeds and capacity not found in the 5G the carrier offers in lower band spectrum.