America's fastest mobile network is getting faster. Verizon today announced that it's speeding up its LTE network, to theoretical maximum speeds of 300Mbps, using a technology known as three-carrier aggregation.

Carrier aggregation bonds together separated lanes of spectrum so they can be used as one, wider lane. AT&T and Sprint have been officially using 2x carrier aggregation, bonding two kinds of spectrum, for a while now; Sprint branded it "LTE Plus." The real news is that Verizon is the first to do a large-scale rollout of 3x carrier aggregation (3xCA), although it's neatly hiding the technology's wide availability.

We've seen 3xCA in action on the Bell network in Toronto, and we've been duly impressed: real-life speeds of 200Mbps or more are definitely possible. Of course, that often only means you can exceed your monthly data cap in minutes. But more speed, and more capacity, are always good things.

So it's important that Sprint and T-Mobile, both of which offer unlimited data, are also publicly working on 3xCA; Sprint demonstrated it in Chicago this week, and Redditors have seen the technology in the wild on T-Mobile. Verizon isn't necessarily that far ahead of the competition.

Verizon confirmed that it's using 2x carrier aggregation in most cities, and 3x in some, although it didn't specify which are which. In 2xCA markets, the company says it's shooting for a maximum of 225Mbps, and with 3xCA, it can hit 300Mbps. The first variety bonds 700MHz and 1700MHz spectrum, both of which Verizon has been using exclusively for LTE. The second variety gets even faster by adding 1900MHz spectrum. But Verizon is still using 1900MHz in some places for 3G.

The width of the individual bands also matters a lot for speed. As carriers have different amounts of each band of spectrum, they end up with different width pipes when they merge them together. It also matters how high-frequency those pipes are. Sprint, for instance, has a huge amount of spectrum, but much of it is at a very high frequency, which has proven hard to deploy over long distances.

The important takeaway: everyone's getting faster, and with 3xCA, 200Mbps is in sight for everyone.

But You Need the Right Phone

There's another twist, as well. Not all phones support 2xCA, and even fewer support 3xCA. Even worse, Verizon actually has 3xCA turned off in the phones which support it.

Most current phones, including the iPhone 6s generation, support 2xCA—Verizon has a list on its website. Those are also called Category 6 phones.

But only a more limited set supports 3xCA. That includes Samsung's Galaxy S7, Note 5, and Note 7, the S6 Edge+, and the HTC 10. The next iPhone, to be announced on Sept. 7, as well as the LG V20, coming on Sept. 6, are widely expected to support 3xCA. Those phones are also known as Category 9 (or higher.)

Verizon says it's working on firmware updates for phones that support 3xCA, and hopes to push them out soon.