For the past couple years, I've been a Verizon user with a deep seething hatred for Verizon. I won't get into why I despise them here, other than to say it's been for both real-world practical and ideological reasons. But, for various reasons also not worth getting into (such as other people on my group plan, and one particular catch involved in the "We'll pay your early termination fee" deals that's personally a show-stopper for me), and let's face it, there's no such thing as a good telecom company, I've been stuck until now.
I've been eyeing T-Mobile a lot lately. I'm not sure sure about the whole "uncarrier" moniker, but they do appear to be an improvement over Verizon in many ways. And from what I can tell, they seem the least offensive and questionable of all the options available here in the US.
However, as anyone who's looked into them knows, T-Mobile's famous Achilles heel has always been questionable service coverage. Aaaaannd...that leads straight down a rabbit hole: This year, T-Mobile's been saying a lot about their greatly improved network. Some users confirm it, some contradict it, and others just ramble about..."band 12"??? WTF is that??? Who even wants to know?!
After researching more and more, I think I've finally gotten a handle on just what is going on with T-Mobile's network lately. Here's what I've found out:
"If you haven't tried our network lately, you haven't tried it period." - Frequent T-Mobile tagline
Turns out, there's a lot of truth to that statement...depending on your phone. But back to that in a bit...
Ultimately, the key concept here is that there's two types of radio frequencies used by cellular carriers: Higher frequencies and lower frequencies.
Lower frequencies travel farther and do a good job of penetrating walls and buildings (See what FCC Chairman Tom Wheeler said about this last year). But there's a downside: They can't handle quite as many people at the same time. So the carriers have to make up for that by building more cell towers. This works out perfectly for the larger carriers who can afford it. In fact, for many years, and up to at least as recently as one year ago, "AT&T and Verizon control nearly three-quarters of low-band spectrum in the US".
Higher frequencies can support more users doing more things at the same time. This makes it attractive to underdogs carriers like T-Mobile who use it because they can support more customers with fewer towers at a lower cost. But the downside is that higher frequencies don't travel as far, and have trouble penetrating walls and buildings. So, historically, T-Mobile has been making do with fewer towers, each with less range. This is why T-Mobile's network works great when you're in range (their higher frequencies can handle more people and more data), but also why actually getting a signal could be difficult (their higher frequencies, from fewer towers, don't travel as far or go through as many walls and buildings).
This past year, T-Mobile's been spending large amounts of money to do two things: First, they've been building new towers to help compensate for their signals not traveling as far as Verizon's. This gives them coverage across a much larger portion of land than before, and fills their coverage map with far more of their flagship pink. This is why some T-Mobile users, particularly ones in suburban areas, have been reporting their coverage has improved. (Although, rural areas are still lagging - albeit not by quite as much as before.) But, since high-frequency is still high-frequency, these additional towers alone don't do much to solve the problem of getting a good signal indoors, or around many large buildings. This is why other T-Mobile users, especially ones in urban areas, have been reporting they're still getting spotty coverage.
Addressing that is the second big thing T-Mobile has been working on recently. Early last year, they spent $3 billion buying a chunk of lower-frequency (700MHz) spectrum from Verizon, and have been bringing it live this year, especially over just these last few months, and they're continuing to utilize more of it even now. They also plan to buy even more (600MHz) at an FCC auction early next year.
This lower-frequency 700MHz range that T-Mobile bought from Verizon and has now been bringing live is what they're calling "Extended Range LTE". In more technical circles, this specific section of 700MHz is also known as "band 12".
But if T-Mobile now has all this new "works well indoors and through buildings" capability, why have some users been reporting they still get bad indoor coverage? They're probably on an older phone: Older phones are, well, older, and so don't support T-Mobile's new "band 12"/"700MHz"/"Extended Range LTE". For reference, here's the current list of phones which do support it. The list is also available here. (Unfortunately, that does exclude the phone I wanted, the Note 3. Damn. So long USB3 and hardware menu button :/ ). But it seems safe to expect all major current and upcoming phones to support it moving forward.
So, bottom line: T-Mobile is currently in the middle of a big shift improving their coverage. Some of this is already here, particularly in suburban areas, but some is still yet to come. The big caveat is that the improvements to indoor reception require a newer phone compatible with T-Mobile's new "band 12"/"700MHz"/"Extended Range LTE".