There are a growing number of voices arguing that the future of 5G will involve spectrum sharing to some degree. But one of the first commercial implementations of dynamic sharing technology in the world – in the 3.5GHz CBRS spectrum band in the US – is now also the scene of an increasingly contentious debate about the effectiveness of that technology.

And while both sides in the debate acknowledge that improvements to the technology can be made – and that operations in the CBRS band are working – the situation nonetheless highlights the difficulties involved in bringing new technologies to market.

Hanging in the balance are wide swaths of spectrum that could be devoted to 5G networks in the future, if spectrum sharing is more widely embraced. That's important considering 5G operators continue to clamor for more spectrum, arguing wireless networks are only as capable as the amount of spectrum supporting them. After all, spectrum is a finite resource – most of it is already used for one application or another, and there's no way to make more.

Thus, if spectrum sharing can't be effectively implemented, 5G operators might have to make do with only those spectrum licenses they can get exclusive access to.

ESC pros and cons

At issue are the Environmental Sensing Capability (ESC) networks installed around the US coastline to look for US Navy communications in the 3.5GHz CBRS spectrum band. If they discover such communications, they alert Spectrum Access System (SAS) managers to immediately move commercial users off that portion of the band.

There are currently two ESC networks in the US: one jointly operated by Google and CommScope and another operated by Federated Wireless.

Google – one of the companies that pioneered spectrum-sharing technology in the CBRS band – has begun arguing that ESC networks aren't particularly effective.

"The primary deficiency of sensing networks is that the need to protect the sensors from interference prevents nearby utilization of the very band that the networks are designed to support," the company wrote to the FCC. "This is especially problematic if an ESC network operator is not rigorous in its choice of sensor deployment locations, and puts them in areas with strong commercial demand."

Google argued that the US government should develop a new sharing technology, dubbed incumbent-informing capability (IIC), that would handle sharing across the entire 3GHz band, including in the 3.5GHz CBRS portion.

But Federated, the other ESC operator, doesn't share that view.

"Deploying a sensor network is preferable and necessary due to the operational risk introduced by deploying an IIC," wrote Kurt Schaubach, Federated's CTO, in response to questions from Light Reading. "IICs require manual input and maintenance, and so introduce the possibility that the largest commercial networks might be taken down by simple human input error."

Schaubach explained that Federated would support a "foolproof," automated IIC capability, but he said such technology would take at least two-three years to develop.

"As with any futuristic endeavors, the question is whether we want to do nothing while we wait. Would we want to park all of our gas cars while we wait for everyone to have electric?" he asked. "Do we want to shut down shared spectrum while we wait for an IIC? Obviously not."

Schaubach then took direct aim at Google and CommScope's ESC and SAS offerings, which Federated competes against.

"Our ESC network has been deployed nationwide since May 2019, with live commercial traffic since September 2019. Since then, we have been working to eliminate false positive data, and greatly reduce the impact of the ESC network itself on commercial CBRS use," he wrote. "We are not seeing the problems that Google cites in their FCC filing. We have heard from customers that Google is having massive problems with the sections of their ESC network that they have only recently deployed, so we believe that's the root cause of their objection. Many customers who are deploying along the coastlines are switching to our SAS/ESC for just this reason."

Operators splitting on ESCs

Some 5G network operators are embracing sharing in the CBRS band. For example, as Light Reading reported in 2019, Verizon for years has been deploying CBRS equipment in anticipation of using the band for commercial mobile operations.

Indeed, the operator spent almost $2 billion in the FCC's CBRS spectrum auction this summer for licenses in locations around the country.

And just this week, Verizon CTO Kyle Malady said the operator already counts "a few thousand" CBRS nodes in its network, mostly running through the operator's growing small cell network.

"We see it as multipurpose spectrum," he said, explaining that most of Verizon's CBRS operations are for outdoor services, but some are for indoor services. He said CBRS spectrum allows Verizon to quickly add more capacity to its network.

Other operators aren't so enthusiastic about CBRS. For example, one of AT&T's top executives wrote in October that "we are learning that the sensing capabilities that are the foundation for true dynamic assignments are falling short of delivering as promised."

And AST Telecom, which operates a wireless network under the BlueSky brand in American Samoa, spent several thousand dollars on CBRS spectrum licenses in its coverage area. "However, BlueSky will not be able to use this spectrum because no Environmental Sensing Capability (ESC) has been deployed on American Samoa," the operator complained to the FCC.

Regardless, there's still plenty of interest in the CBRS band. For example, a new report from SNS Telecom & IT predicts annual investments in LTE and 5G in the CBRS band will pass $1 billion by 2023. And Paris-based Red Technologies is applying to become an ESC operator in the US.

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— Mike Dano, Editorial Director, 5G & Mobile Strategies, Light Reading | @mikeddano