It's been a little more than a year since T-Mobile USA bought enough 600MHz spectrum licenses to cover the entire country, and the carrier has now activated the spectrum band in more than 900 cities and towns in 32 states. In 120 of those cities and towns, it's the first time T-Mobile has offered LTE coverage, the company said in an announcement yesterday.

Only a few Samsung, LG, Motorola, and OnePlus phones are capable of using the new spectrum today, but 600MHz support should eventually become a common feature in new phones. It will also take multiple years for T-Mobile to fully deploy the spectrum across the US.

T-Mobile bought this low-band spectrum because it's ideal for covering long distances and penetrating obstacles such as building walls, which have long been problems for T-Mobile's network.

"T-Mobile's Extended Range LTE signals travel twice as far from the tower and are four times better in buildings than mid-band LTE, providing increased coverage and capacity," the company said.

T-Mobile needed the 600MHz spectrum to catch up to AT&T and Verizon Wireless, especially in rural areas. An advertising industry self-regulatory body recently told T-Mobile to stop claiming it has the "best unlimited network." While some speed tests give T-Mobile a leg up over competitors, network studies by RootMetrics show that T-Mobile lags rivals in overall coverage and reliability.

T-Mobile's coverage in big cities was already pretty strong, so it's no surprise that early 600MHz deployments are filling gaps outside the big cities. For example, T-Mobile has deployed 600MHz in California but not in Los Angeles; in Michigan but not in Detroit; in Pennsylvania but not in Philadelphia or Pittsburgh; in Texas but not in Dallas or Houston; and in New York State but not in New York City. The full list of cities and towns with 600MHz deployments was available at this link, but the link appears to be broken now.

T-Mobile said it will bring 600MHz coverage to Puerto Rico this fall.

First phones to support 600MHz

Most smartphone users won't be able to use the 600MHz spectrum today because device manufacturers have to add support for new spectrum bands. As of now, the 600MHz network is compatible with the Samsung Galaxy S8 Active, Samsung Galaxy S9, Samsung Galaxy S9 Plus, four LG phones, the OnePlus 6, and at least one Motorola phone. More than a dozen 600MHz-capable phones "across all price points will launch by the end of this year, T-Mobile said.

Despite today's limited options, the deployment will help T-Mobile in future years as device manufacturers add support. Apple didn't include 600MHz support in the iPhone 8 and iPhone X released last year, and it's not yet clear whether new iPhone models to be released later this year will support the spectrum band.

T-Mobile was already using 700MHz spectrum in addition to mid-band spectrum such as 1700MHz, 1900MHz, and 2100MHz. But T-Mobile says that its 600MHz haul in last year's spectrum auction tripled its low-band spectrum holdings. T-Mobile is licensed to use an average of 31MHz within the 600MHz spectrum band in each geographic area. T-Mobile uses the "Extended Range LTE" label for both its 600MHz and 700MHz spectrum deployments.

"Immediately after receiving the licenses—less than a year ago—T-Mobile began its rapid 600MHz Extended Range LTE rollout," T-Mobile said. "To accelerate the process of freeing up the spectrum for LTE, T-Mobile is working with broadcasters occupying 600MHz spectrum to assist them in moving to new frequencies."

T-Mobile still has plenty of work to do. There are more than 19,000 cities, towns, and other incorporated places in the US.

While T-Mobile's LTE network already covered more than 300 million Americans, the carrier hasn't revealed how many Americans live in the areas where it has deployed 600MHz spectrum. We asked T-Mobile for more details on the scope of its 600MHz deployment and will update this story if we get a response.

UPDATE: T-Mobile declined to say how many Americans are covered by the 600MHz deployments, but said it is focusing on rural areas. "We started deploying 600MHz first in rural areas where we have the opportunity to expand our coverage and bring choice and competition to consumers with this spectrum," T-Mobile told Ars. "We are starting with areas of the country where we don’t already have 700MHz spectrum."

The 600MHz deployments thus far are in Alabama, Arizona, Arkansas, California, Colorado, Idaho, Illinois, Iowa, Kansas, Maine, Michigan, Mississippi, Missouri, Nebraska, New Jersey, New Mexico, New York, North Carolina, North Dakota, Oklahoma, Oregon, Pennsylvania, South Carolina, South Dakota, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, and Wyoming.

T-Mobile is trying to buy Sprint, arguing that the companies need each other in order to build a competitive 5G network. But T-Mobile already said it was on track for a strong 5G deployment even before announcing plans to buy Sprint.

The ongoing 600MHz deployment will also help T-Mobile upgrade to 5G because the carrier says it's using "5G-ready equipment" for Extended Range LTE. T-Mobile can thus enable 5G "with the flip of a switch without having to touch towers twice," the company said last year.