T-Mobile and Sprint are taking the first steps toward combining their networks after the two companies completed their landmark merger earlier in April. T-Mobile customers in Philadelphia and New York City are set to be the first to get access to Sprint’s 2.5GHz mid-band 5G network in addition to the existing 600MHz low-band and mmWave high-band 5G networks T-Mobile has already launched.

In addition to the 5G expansion, T-Mobile is also opening up its LTE network to Sprint customers to use when roaming, which it says should open up “more than double the number of LTE sites” than Sprint’s current network.

Philadelphia — which, right now, only has 600MHz 5G — will get access to Sprint’s higher-bandwidth (and faster) network today, while New Yorkers will get access to the mid-band network “soon,” according to Karri Kuoppamaki, T-Mobile’s VP of radio network technology and strategy.

The 5G expansion isn’t as simple as just flipping a switch since the 2.5GHz 5G network (like nearly all 5G right now) is a non-standalone network, meaning that it relies on existing 4G hardware to work. So in order to give T-Mobile users access, the company has to set up new antennas at its existing T-Mobile cell sites. For the original nine cities in which Sprint had its 5G network active, that means shutting down the old Sprint antenna and setting up new T-Mobile ones — a process it has already begun in New York City. All future 2.5GHz rollouts, like the Philadelphia deployment, will just take place on T-Mobile’s network.

Older Sprint phones will eventually lose access to 5G networks entirely

The new 2.5GHz network will be available to T-Mobile users who own compatible phones, a list that includes the Galaxy Note 10 Plus 5G, the OnePlus 7T Pro 5G McLaren, the various Galaxy S20 phones, or the newly announced OnePlus 8 and 8 Pro.

On the flip side, with that mid-band network shifting over to T-Mobile customers, current Sprint 5G customers will start to be left out in the lurch. Newer phones — like the Sprint versions of the Galaxy S20 lineup — that can access T-Mobile’s low-band network will apparently be shifted over to there, too. (T-Mobile’s announcement has yet to clarify whether other newer Sprint devices, like the OnePlus 8, will get similar access going forward.)

Eventually, older devices (like the Sprint OnePlus 7 Pro 5G, Galaxy S10 5G, and LG V50 ThinQ 5G) will lose access to 5G networks entirely as T-Mobile takes over the spectrum, although PCMag notes that those owners should get an offer to switch to a newer T-Mobile 5G device.

While this is all somewhat complicated, it’s the first realization of T-Mobile’s long-term 5G strategy, which looks to combine a wide variety of spectrum and network types to achieve a mixture of broad coverage and high speeds. The foundation of the New T-Mobile’s 5G network is the 600MHz low-band network that T-Mobile launched on a nationwide level last fall. That network has the broadest reach of any 5G network so far, thanks to the fact that it effectively operates in the same airwaves as LTE, augmented with new technology for faster speeds. On the flip side, though, that wide coverage also means that it’s the slowest form of 5G around.

The first realization of T-Mobile’s long-term 5G strategy

T-Mobile also has a mmWave network, similar to AT&T’s “5G+” network and Verizon’s entire 5G plans so far. Operating up in the 28 GHz and 39 GHz range of the spectrum, mmWave 5G offers dramatically faster speeds than anything else. The downside is that (as we’ve already seen with early testing) mmWave technology also suffers from extremely short range and a poor ability to pass through walls. Thanks to that shorter range, T-Mobile’s rollout for mmWave 5G is far less comprehensive than its low-band network, which is launching in just a few cities. And even where it has launched, coverage for the mmWave network is far smaller than the low-band option.

The last piece of the puzzle, starting to be integrated in today, is Sprint’s 2.5GHz network, which is somewhere in between the 600Mhz low-band and mmWave portions. With speeds that are faster than T-Mobile’s existing low-band network but with a better range than the mmWave network, it offers a good middle ground for 5G with fewer compromises. Prior to the T-Mobile acquisition, Sprint had rolled out its network in parts of nine cities: Atlanta, Chicago, Dallas-Fort Worth, Houston, Kansas City, Los Angeles, New York City, Phoenix, Washington, DC. A 10th city, Philadelphia, started its 2.5GHz rollout on April 1st when the acquisition was announced.