Fiascos with FAA, Ligado spur new look at receiver standards

At the most basic level every communication system has a transmitter than sends out energy and a receiver that picks up that energy and sorts it out. You could call this “Radio Technology for Dummies.”

And one would think that since the radio was invented more than 100 years ago, that receiver technology would be quite refined. But sometimes electronics manufacturers, in order to save money, don’t build the highest-quality receiver technologies into their devices. As a result, cheap receivers can pick up interference from out of their spectrum bands.

In the U.S. this issue has been debated for many years with one camp desiring stricter receiver standards and a different camp — including electronics manufacturers and some federal users — opposed to more stringent standards.

But in recent years, there have been a couple of major events related to receivers, causing the issue to raise its head once again.

There is the big dispute between the Federal Aviation Administration (FAA) against Verizon and AT&T. The carriers spent tens of billions of dollars on C-band spectrum. And then just when they were about to deploy it for 5G usage across the country, the FAA said use of the spectrum near airports could potentially cause plane crashes.

The crux of the matter is that many airplanes are outfitted with older altimeters. These altimeters do not use C-band spectrum. However, they weren’t designed to strictly stay in their own lane, and they can pick up interference from C-band. The FAA is now scrambling to make sure older altimeters are replaced with more precise equipment.

The second major dispute is the conflict between Ligado against the Department of Defense (DoD) and the GPS industry.

Ligado Networks, formerly known as LightSquared, wants to use spectrum it owns in the 1526-1536 MHz band for terrestrial 5G wireless telecommunications. But the DoD and GPS companies say that use of the spectrum could cause interference to their receivers.

The National Academy of Sciences plans to release a report on September 9 evaluating Ligado’s potential impact on GPS and DoD activities.

Dale Hatfield, senior fellow at the Silicon Flatirons Center, told Fierce, “The GPS industry is claiming they’re getting interference. But the interference they’re most worried about is way outside their assigned channel. If they had better receivers they would receive only their frequencies.”

FCC steps in

In April, the Office of Engineering and Technology at the Federal Communications Commission (FCC) opened a Notice of Inquiry regarding the improved use of radio receivers to prevent interference. The FCC is interested in comments on the topic because it wants to ensure that the nation’s spectrum is used most efficiently.

In comments filed by Commissioner Geoffrey Starks, he said, “This Notice of Inquiry has been a long time coming. Nearly 20 years ago, the Commission took its first hard look at addressing the issue of receiver performance. Unfortunately, a wide variety of factors ultimately caused that proceeding to close without final action. Ten years later, there was yet another attempt at the issue of receiver performance, but once again, no final FCC action took place, even as our spectrum demands grew. This continued surge in spectrum usage has now brought us here, and it’s high time to reopen our inquiry into a whole-of-system approach to spectrum management.”

Preston Padden, a longtime telecom executive who is now principal of the consulting firm Boulder Thinking, is passionate about updating receiver standards. In a filing with the FCC recently he wrote, “As spectrum becomes more scarce, and demand increases, our system of spectrum licensing will collapse unless the FCC adopts strict receiver standards.”

In a previously published column with Fierce Wireless, Padden provided charts that show how airline altimeters are licensed for a discrete band of spectrum, but their receivers actually receive signals from far over into other people’s territory.

Speaking with Fierce, Padden said, “How can we go forward where people get licensed for one set of frequencies but then deploy receivers that squat over others’ spectrum?”

Asked why he cares so much about receiver standards, Padden said, “I am naturally attracted to Don Quixote battles.” He said he was involved with the C-Band Alliance before the spectrum was auctioned and was involved in conversations with the FAA, showing them the“enormous guard band that was going to protect their radio altimeters.”

One of Padden’s children, Joey Padden, is a principal at the firm FreedomFi, which does offloading of cellular traffic onto CBRS networks.

Padden said his interest in receiver standards has nothing to do with FreedomFi. “The world that FreedomFi lives in is governed by 3GPP, and they have very strict standards for frequency-specific receivers in all 3GPP-approved devices,” he said. “Why does the FCC not require the same strict standards for other devices like the 3GPP requires for mobile wireless devices?”

CTA's perspective

Not everyone is gung-ho about stricter receiver standards. 

In comments filed by the Consumer Technology Association in June, the group suggested some possible solutions to the receiver problem should include relying on voluntary industry standards and issuing high-level policy statements. “The cornerstone of any new spectrum policy should be flexible, marketplace-driven standards with minimal government requirements and preservation of user opportunities to quickly implement innovative technologies,” it wrote.

To put a fine point on it, CTA added, “The Commission should not adopt government-mandated receiver performance standards or interference thresholds.”

In his FCC comments, Padden wrote, “Apologies in advance to my longtime friend Gary Shapiro, the esteemed CEO of CTA/CES, who has made it his life’s work to prevent the government from telling his members how to build their equipment.”

But the fiascos with the FAA and Ligado may have shifted the winds in favor of stricter standards.

FCC Commissioner Nathan Simington has been a leading advocate for updated receiver standards. In comments he filed in April Simington said, “The era of abundant spectrum is coming to a close. Like real estate, they just aren't making any more of it. The future is dense spectral neighborhoods of commercial users packed tightly, in space and in spectrum, vying for every last hertz of usable real estate.”

And he added, “We cannot afford the next C-Band fight. This item takes a first step toward foreclosing that eventuality.”