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One of the biggest questions surrounding T-Mobile’s plan for a nationwide 5G network based on low-band 600MHz spectrum is being answered today, as the third-largest U.S. carrier announced successful completion of the “world’s first 5G call on 600MHz” — a meaningful but obscure milestone on its path to offering 5G service. The achievement used Intel’s 5G Mobile Trial Platform, which appears to be the first hardware identified as capable of offering 5G service over that low-frequency spectrum.

Up until now, almost all of the discussion about 5G networks has focused on high-band millimeter wave spectrum in 24-39GHz frequencies, and mid-band spectrum in 3.5-6GHz frequencies. But T-Mobile has repeatedly underscored its interest in offering 5G service on a much lower 600MHz spectrum, radio signals that are capable of reaching much further in distance: The new 5G test signal could reach “more than a thousand square miles from a single tower,” the company says. As of now, towers with the 600MHz hardware are already live in over 1,500 cities and towns in 37 states, offering 4G service that can be switched to 5G as needed.

A major caveat has been that a lower-frequency spectrum is likely to be saddled with slower data speeds and the potential for greater latency — both contrary to 5G’s key goals. T-Mobile’s (likely to be acquired) rival carrier Sprint has similarly said that its 5G service would be built on 2.5GHz spectrum, closer to mid-band but still likely to be slower. T-Mobile offered no data speed information for its successful 5G call but said that it had also completed a tri-band 5G video call with users on 600MHz, 28GHz, and 39GHz spectrum bands.

The key question has been who would actually supply the 5G hardware necessary to empower the low-band 5G vision. T-Mobile initially signed a $3.5 billion deal with Nokia for tower hardware in late July. Then in September it signed a similar deal with Ericsson, which participated in the new 600MHz test. On the device side, however, current 5G chip leader Qualcomm has seemingly been focused primarily on developing tiny chips and antennas for millimeter wave and sub-6GHz devices, which are expected to appear in 5G devices this year for Verizon’s and AT&T’s networks, along with those of some Asian carriers.

By contrast, Intel has been working on a second-generation 5G chipset that will better compete with Qualcomm’s offerings — and apparently cater to different customers. Today’s announcement suggests that T-Mobile may, as Apple is reportedly doing, rely on Intel to cater to its special needs.

“5G will power vibrant new use cases that span across network, client, and cloud,” said Intel SVP Sandra Rivera. “This collaboration with Ericsson and T-Mobile conducted over low-band spectrum and using the Intel 5G Mobile Trial Platform is a major milestone on the path to enabling the first wave of these types of 5G experiences.”

T-Mobile will likely have more to say on its 5G plans at CES 2019 this week. Though the carrier says it is embracing a multi-frequency strategy that will include low-band, mid-band, and high-band millimeter wave support, it will offer live 5G demonstrations at CES to “show attendees how low-band spectrum is able to penetrate physical barriers like windows and doors,” while millimeter wave signals cannot. Having previously promised early 5G rollouts in 2019, the company maintains it will offer nationwide 5G coverage in 2020.

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