AT&T told the FCC it may want to test 5G NR-U technology working in the unlicensed 6GHz band. The company's request could potentially signal the operator's interest in pushing its 5G operations in its licensed spectrum into the unlicensed 6GHz spectrum band.

Such a move already has precedent; several years ago, the US wireless industry pushed for regulatory approval to transmit 4G signals in the unlicensed 5GHz band via Licensed Assisted Access (LAA) technology.

"Applicant seeks to study the functionality and capabilities of U-NII-5 and U-NII-7 equipment operating under the IEEE 802.11ax/WFA Wi-Fi 6E standard or the 3rd Generation Partnership Project ("3GPP") LTE-LAA/5G NR-U standard," AT&T wrote in its testing request to the FCC. "Testing will explore the potential for interference and co-existence with incumbent licensed fixed services in these U-NII-5 and U-NII-7 bands and provide valuable information as to performance, feedback to regulatory and standard bodies enabling future standards improvement and system optimizations. Testing is to occur in and around the AT&T Center for Learning, 6301 Colwell Blvd, Irving, Texas 75039."

Network operators like AT&T typically do not comment on their testing ambitions beyond their FCC applications.

AT&T's request touches on a wide range of recent developments in the wireless industry, as well as operators' general interest in adding capacity to their wireless networks.

First, it acknowledges the importance of the massive amount of spectrum in the 6GHz band. The FCC voted last year to release fully 1200MHz of spectrum in the 6GHz band for unlicensed uses like Wi-Fi. That vote represented a bit of a slap against the global 5G industry, which has lobbied regulatory agencies like the FCC to set aside at least a portion of the 6GHz band for licensed operations, including 5G.

Due to the FCC's decision to retain the entire 6GHz band for unlicensed operations, it appears some operators – including Verizon and now AT&T – may still be interested in using the band for their 5G services. To do so, they may use a technology similar to LAA. That technology traces its origins back to 2013, when 4G proponents began proposing ways for 4G operations in licensed spectrum to expand into unlicensed spectrum bands to increase operators' overall network capacity. The FCC eventually approved the use of LAA technology in the 5GHz unlicensed spectrum band, over objections from the Wi-Fi industry. (Importantly, new research cited by FierceWireless shows that 4G LAA technology could degrade the performance of Wi-Fi in the 5GHz band.)

Now, AT&T and others may be looking to employ a similar approach to 5G in unlicensed spectrum bands. They may hope to do so via the new 5G NR-U standard approved by the 3GPP last year. 5G NR-U is essentially the 5G version of LAA.

Finally, there's one more element at play in AT&T's testing request. The company already uses the 6GHz band to backhaul some of its cell sites – such operations were widespread in the band before the FCC opened it up to unlicensed operations. Indeed, AT&T has opposed unlicensed operations in the 6GHz band over fears they might interfere with its backhaul operations.

Recently, the FCC began accepting applications for Automated Frequency Coordination (AFC) systems in the 6GHz band. AFC systems are designed to support standard-power transmissions in the band that won't interfere with existing 6GHz users, such as those already using the band for cell site backhaul or radio astronomy. Companies, including Qualcomm, Federated Wireless and others, hope to operate AFCs.

AT&T told the FCC it would use "pre-AFC certified experimental equipment" for its tests, alongside Wi-Fi 6E routers from the likes of Samsung, NetGear and ASUS.

Figure 1: In its FCC request, AT&T said it would conduct tests outside and inside. Click here for a larger version of this image.
(Source: AT&T)

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