AT&T to deploy dynamic spectrum sharing in second half of 2020

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AT&T's Igal Elbaz said DSS is a "profound technology" that lets the carrier transition to 5G very efficiently. (Getty Images)

Verizon has probably been the carrier most vocal about benefits of dynamic spectrum sharing (DSS) technology, but rival AT&T is also a fan and SVP Igal Elbaz said Thursday that the carrier expects to deploy DSS later this year.

“You should expect us to have DSS introduced in our network in the second half of 2020,” said Elbaz, AT&T’s senior vice president of Wireless Technology, speaking this morning to investment analysts at the virtual Cowen and Company Technology, Media & Telcom Conference.

Elbaz called DSS a very important technology in terms of enabling both AT&T and other carriers to scale 5G rollouts.

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The timeline is similar to that of rival Verizon, which has pointed to dynamic spectrum sharing as key to its strategy for introducing broad nationwide 5G coverage this year using existing spectrum. Last month CEO Hans Vestberg indicated Verizon’s plans to commercially deploy DSS in the second half of this year are still on track, with no COVID-19-related supply chain issues affecting the carrier’s ability to do so.

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Dynamic spectrum sharing allows carriers to operate both 5G New Radio (NR) and LTE using the same spectrum channel by shifting or allocating resources between the two, based on the number of users or traffic needs.  

This is different from previous technology generation shifts, where carriers usually had to carve out or take away a portion of their existing spectrum and dedicate it to the new technology. Elbaz used the example of having four channels for LTE, and then needing to take away one channel, clean it, and use it only for 5G. That leaves an operator with only three channels instead of four for the vast majority of its users who are still on LTE. Meanwhile, there’s a free channel for 5G, but it has very little usage because it takes time for new 5G users with capable devices to accumulate and generate traffic.

“That’s not an efficient way to manage your spectrum in the transition,” Elbaz said.

AT&T and T-Mobile have each already rolled out low-band 5G service that’s not much speedier, or in some cases slower, than 4G LTE. Verizon, which is seen as lacking in low- and mid-band spectrum that it can dedicate to 5G, has stuck to 5G deployments using millimeter wave spectrum limited to small pockets of urban areas. Verizon is expected to participate for mid-band spectrum at the C-band auction set for December, but it will take time before that can be put to use.

While DSS will let the carriers use existing spectrum to roll out 5G more quickly, it’s been observed that the technology doesn’t add extra capacity.

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Analysts at LightShed Partners have said they expect Verizon will deliver broad 5G coverage enabled by a combination of DSS and carrier aggregation. As the firm explained, despite the confusing name, carrier aggregation enables operators to combine spectrum blocks, both blocks adjacent and non-adjacent, and from other bands to deliver faster speeds to end users.

Although AT&T is pursuing a $6 billion cost-cutting initiative, Elbaz reiterated that AT&T will continue to invest in its core products, which include 5G, fiber and HBO Max (which just launched yesterday). That includes likely participation for C-band spectrum. Still, Cowen analysts today suggested DSS could mean the carrier doesn’t need to invest in as much new spectrum as it would otherwise.

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While preparing for its 5G deployments, AT&T has bolstered its 4G LTE network, adding capacity with nearly 160 MHz of sub-6 GHz spectrum alongside its FirstNet public safety build. Network testing results tracked significant 4G LTE performance increases following enhancements that included additional spectrum and LTE-Advanced technologies such as carrier aggregation.

AT&T stands out as the only carrier able to utilize 5-carrier aggregation on a wide scale for 4G LTE. According to RootMetrics, that helped boost AT&T’s speed performance significantly in 51 out of 55 markets tested in the first half of 2020, compared to the end of 2019. Comparatively, for 4G LTE, Sprint and T-Mobile use 3-carrier aggregation, while Verizon uses 4-component carrier aggregation. Support for 5G carrier aggregation is expected in June with 3GPP Release 16.

With DSS, AT&T can use existing channels for 5G, sharing instead of sacrificing 4G LTE spectrum resources. As more 5G devices come online, carriers can deploy DSS on additional, or eventually all, existing channels to serve both 4G LTE and 5G users.  

“[DSS] is a profound technology and really allows us to do that transition very efficiently,” Elbaz said.

RELATED: Ericsson defends dynamic spectrum sharing

That said, there is at least one carrier that has cast some doubt on DSS. Last month T-Mobile President of Technology Neville Ray reiterated that one vendor was still trailing in a DSS product; T-Mobile doesn’t depend DSS for its nationwide 5G network thanks to its 600 MHz portfolio.

Ericsson led the charge on dynamic spectrum sharing technology, and its product is already being commercially used by global operators, including Swisscom, Telstra, and Play. Nokia, meanwhile, launched DSS in April, with volume shipments anticipated in July in line with availability of DSS-capable handsets.

While Ray called DSS “still bumpy”, he acknowledged T-Mobile will still deploy it. Verizon and AT&T executives have refuted problems with DSS, including Verizon’s Vestberg, who last month said tests were going “very well.”

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