Licensed spectrum remains perhaps the most important building block of the wireless industry. As a result, nationwide carriers like Verizon, AT&T, T-Mobile and Sprint are eager to both obtain suitable spectrum holdings across the country, and to use those spectrum licenses in the most effective way possible.

But where exactly do these nationwide carriers own spectrum? And how much spectrum do they own?

To answer these questions, FierceWireless has once again partnered with Allnet Insights & Analytics, a wireless spectrum research and analysis firm, to map out exactly how much spectrum each of the four Tier 1 nationwide U.S. wireless carriers currently has that it can deploy for LTE service, broken down on a county-by-county basis. According to Allnet President Brian Goemmer, a wireless industry veteran with 20 years of experience, AllNet has developed what it calls "Download Spectrum Depth Maps" to represent the available LTE spectrum for each of the Tier 1 carriers based upon their current LTE deployment configurations. The maps are based on a September 2016 data set.

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The maps represent the downlink spectrum that matches the latest handsets that are available for each carrier.

Essentially, these maps show how much spectrum each of the nation's Tier 1 carriers currently has for LTE based on their stated LTE deployment plans. To be clear, these maps don’t show actual LTE deployments, only the spectrum that likely is used or will be used for LTE deployments. The maps have been structured so that the total spectrum deployed for three-carrier aggregation is shown on the first map, with the following maps indicating the contribution from each frequency block. The maps also do not include spectrum bands that the carriers control but are not in use for LTE (such as the cellular bands carrying voice traffic for both AT&T and Verizon).

Scroll down for maps for Verizon, AT&T, Sprint and T-Mobile. Click on any image to enlarge it.

Verizon

Verizon is the nation’s largest wireless carrier with around 143 million customers at the end of the second quarter. The operator’s LTE network covers roughly 312 million POPs. Verizon initially built its LTE network on the 700 MHz spectrum licenses it won in the FCC’s 700 MHz spectrum auction during 2008, and has since bolstered those spectrum holdings via acquisitions of other licensing including AWS-1 spectrum licenses.

Verizon also spent roughly $10.4 billion last year on AWS-3 spectrum licenses; the operator has not made any public comments about when it might start building out those spectrum licenses.

Verizon is also registered to bid in the FCC’s ongoing incentive auction of TV broadcasters’ unwanted 600 MHz spectrum licenses.

As Allnet notes, Verizon’s spectrum carrier aggregation strategy can combine transmissions across its 700 MHz (band 13), PCS (band 2) and AWS (band 4) licenses. Carrier aggregation technology essentially glues together transmissions across various spectrum bands to increase download speeds. Verizon recently announced it is employing two-carrier aggregation and will employ three-carrier aggregation.

Allnet also said that, in counties where Verizon does not have cellular spectrum, no PCS spectrum is utilized for LTE. The firm added that, in counties where Verizon has both A/B band Cellular, all of its PCS spectrum is utilized for LTE. Allnet also said that 50 percent of Verizon’s PCS spectrum can be considered "refarmed" and available for LTE.

AT&T

AT&T is the nation’s second largest carrier with around 132 million customers. The operator’s LTE network covers 355 million people in North America, an area that includes AT&T’s new operations in Mexico. The operator’s LTE network primarily works on its AWS-1 and 700 MHz spectrum licenses, but can also stretch into its WCS holdings and other spectrum bands.

AT&T spent around $18 billion on AWS-3 spectrum licenses last year, and expects to start building those licenses out starting next year. Allnet said it incorporated the largest AWS channel within the expanded AWS band 66 for AT&T. AT&T is also a registered participant in the FCC’s ongoing 600 MHz incentive auction.

As Allnet notes, AT&T’s carrier aggregation strategy generally covers its 700 MHz (band 17), PCS (band 2), AWS (band 66) and WCS (band 30) licenses. Allnet said that AT&T has four bands it uses for LTE; the firm added that, with three-channel carrier aggregation, its only includes the three largest channels.

“Although AT&T has nearly licensed for 100% of the US with the WCS band, there are many counties that we don't include WCS in their 3 carrier aggregation strategy,” Allnet said. “Essentially their PCS channel is 10 MHz or larger in those markets so it is included in the aggregation strategy.”

Allnet also said that, in counties where AT&T does not have cellular spectrum, no PCS spectrum is utilized for LTE. The firm added that, in counties where AT&T has both A/B band Cellular, all of their PCS spectrum is utilized for LTE.

Roughly 50 percent of AT&T’s PCS spectrum can be considered "refarmed" and available for LTE, Allnet said.

T-Mobile

T-Mobile is the nation’s third-largest wireless carrier with around 68 million customers. The carrier’s LTE network covers “nearly” 312 million people. T-Mobile’s LTE network primarily works on its AWS-1 and 700 MHz licenses.

T-Mobile spent around $1.77 million on AWS-3 spectrum licenses, and has said it could start building out those licenses as early as this year. Allnet said it incorporated the largest AWS channel within the expanded AWS band 66 in its maps.

T-Mobile also has said it could spend up to $10 billion on 600 MHz spectrum licenses in the FCC’s ongoing incentive auction.

Allnet said T-Mobile’s carrier aggregation strategy includes 700 MHz (band 12), PCS (band 2) and AWS (band 66), and that 50 percent of T-Mobile’s PCS spectrum can be considered "refarmed" and available for LTE.

Sprint

Sprint is the nation’s fourth largest wireless carrier with around 58 million customers. The operator’s LTE network covers around 300 million people.

Allnet notes that Sprint’s carrier aggregation strategy includes the operator’s SMR/Cellular (band 26), PCS (band 25) and up to 3 -20 MHz channels of EBS/BRS (band 41).

Allnet added that downlink spectrum values (MHz) have been adjusted for Sprint TDD-LTE spectrum (EBS/BRS) since a channel of this spectrum operates for both uplink and downlink. Sprint's stated downlink ratio is 75 percent so a 20 MHz channel nets 15 MHz of downlink spectrum, Allnet said.