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Prior to this year, 5G carrier AT&T had already placed a large bet on the 39GHz millimeter wave radio band, acquiring FiberTower’s sizable 379MHz blocks of spectrum. Today, AT&T confirmed that it has more than doubled its national 39GHz spectrum holdings to 786MHz, on average, a development that should enable the carrier to offer at least 3Gbps download speeds across the country — assuming it has the wherewithal to actually build towers to support the short-distance mmWave holdings.

The considerably faster transfer speeds promised by 5G networks depend on empty spectrums — radio frequencies that aren’t already being used for other purposes. To hasten U.S. 5G development, the FCC has been auctioning blocks of millimeter wave spectrums, and AT&T swapped its FiberTower holdings for auction vouchers, enabling it to target contiguous spectrum blocks across the country. After bidding $2.4 billion, half from vouchers, AT&T won the 786MHz of nationwide 39GHz spectrum, bringing its national mmWave average to 1,040MHz, including separate 24GHz holdings.

Last April, AT&T said its Netgear Nighthawk 5G hotspot hit a 2Gbps peak on its enterprise-focused 5G mmWave network, surpassing the carrier’s initial promises of 1Gbps peaks. But AT&T’s consumer 5G network has been disappointingly slower, offering 4G-like speeds using low band spectrum. Like rival T-Mobile, AT&T has focused its consumer 5G launch on covering large swaths of land rather than on ultimate performance.

Doubling down on 39GHz means AT&T will have 800MHz bandwidth in some markets, enough for eight 100MHz channels. The carrier has previously said it can deliver up to 400Mbps of download speed per 100MHz channel, reaching 1.5Gbps across four channels, suggesting that 3Gbps should be easily attainable through all eight channels. Moreover, if a 5G device can simultaneously access AT&T’s 39GHz and 24GHz spectrums, or the 39GHz spectrum plus low or mid band channels, the speeds could be even higher.

While AT&T now has the spectrum to support a national 39GHz 5G network, its ability to build out the supporting tower hardware remains a question mark. Like other millimeter wave frequencies, a 39GHz signal’s ability to travel is measured in feet rather than miles, requiring significant “small cell” radio hardware deployments to provide service. As such, AT&T has signaled that it will initially use mmWave to provide peak speed “5G+” in dense urban environments, with no specific timeline for wider rollouts elsewhere.

By comparison, rival Verizon has focused almost exclusively on millimeter wave for its initial 5G rollout and has hit peaks in the 2Gbps range. Most of its real-world service has peaked at under 1.5Gbps, however, and the carrier has typically promised ideal performance of 1Gbps with more common speeds in the 600Mbps range.

Today’s announcement notes that AT&T’s 5G+ network is now available in parts of 35 cities and is initially being densified to provide mobile service at “arenas, campuses, and more,” with fixed (home broadband) service potentially to follow. AT&T currently sells only a handful of phones with 5G+ support, including the Samsung Galaxy S20+ and S20 Ultra 5G, but the carrier is expected to broaden its selection later this year.

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