When I wrote about the grim outlook of the AT&T/T-Mobile merger deal in my previous guest post, I brought up an interesting bit of rumor. If the deal had gone through, T-Mobile would have essentially gone away, and its 33+ million customers would either end up with AT&T, Verizon, Sprint, or one of the smaller, regional carriers. However, with T-Mobile safe from AT&T’s clutches (for now), there is not much stopping Apple from bringing the iPhone to T-Mobile customers.

When Apple released the iPhone 4S, the company titled it a “world phone.” This means that the iPhone 4S is able to operate on a variety of networks while utilizing the same hardware. With the previous generation, Apple had to order separate devices for Verizon and AT&T, respectively. Now, it has one phone to rule them all (literally).

The chip behind the iPhone 4S’s “world phone” capabilities is the Qualcomm MDM6610, as determined by iFixit’s teardown of the device. The chipset can support (obviously) AT&T, Verizon, and Sprint’s wireless frequencies. In addition, it also supports the 1700 MHz and 2100 MHz AWS band T-Mobile uses
for its HSPA+ network. In fact, the iPhone 4, which makes use of the MDM6600 chip, supports pentaband UMTS (i.e., it supports both AT&T and T-Mobile 3G networks) according to Engadget’s FCC findings. So basically, there is a very good chance iPhone 4S completely supports T-Mobile’s network at the hardware level. In that case, why don’t you get 3G speeds when you insert your T-Mobile SIM card into your iPhone 4S?

While the support for T-Mobile’s AWS band may exist at the hardware level, the software on the device must still be configured for the appropriate wireless bands. Fixing this isn’t as simple as jailbreaking your iPhone and flipping a setting, however. The configuration for the bands is most likely hard-coded into the firmware on the chip when the device is assembled at the factory. Don’t fret though, as it is usually simple for the manufacturer, in this case Apple, to make the required changes. After all, Apple most likely configures devices depending on whether they will be shipped out to Verizon, Sprint, AT&T, or any of the other carriers the iPhone sails under — what’s one more?

There is the slim chance, of course, that there is another hardware incompatibility that would present a major roadblock to seeing the iPhone reach T-Mobile. If the radio power amplifiers (the Skyworks and Avago chips in the device teardown linked above) are not compatible with the T-Mobile frequencies, then you might hit some difficulties. The model numbers printed on the chips appear to be obfuscated in the typical Apple fashion (for instance, the Apple A4 was literally a re-branded Samsung Hummingbird core), so I was unable to conclude anything looking through the Skyworks and Avago product lists, making it difficult to determine the exact frequencies the power amplifiers deal with. Still, considering the supported frequencies Apple advertises, there is a good chance the hardware is in fact compatible with T-Mobile’s bands.

Nevertheless, if everything is smooth at the hardware level, Apple would easily be able to provide a T-Mobile iPhone by re-configuring the software on the device. I doubt at this point it would cost the company much, considering it is already producing devices with modified software compatible with both GSM-based and CDMA-based networks. What’s more, Apple has everything to gain from the choice.

When it was announced that C Spire Wireless would be the fourth US carrier to receive the iPhone, many people were in a state of shock. After all, why on earth would you pick a regional carrier that serviced less than a million customers over a carrier like T-Mobile, that is 33+ million customers strong? The only answer I can give to that is, of course, the potential threat of a merger with AT&T. Now that the aforementioned deal appears to be dead for good and T-Mobile has openly stated that it is interested in offering the iPhone in its line-up, perhaps we will see Apple waving some magenta colors some time in the future.

I personally know quite a few people who love the iPhone and its simplicity. I know even more people who love T-Mobile’s great plans and service. Based on that, I think I’m safe in saying that a T-Mobile-bound iPhone would be a match made in heaven for quite a few people. I am an Android user myself, but what is good for T-Mobile will benefit me in the long run as well. T-Mobile is known for being generally good to its customers, so odds are it will pass on its good fortune with the iPhone in the form of affordable, quality plans and an improved wireless network.

TL;DR — The iPhone 4S’s wireless chipset, the Qualcomm MDM6610, supports T-Mobile’s 1700MHz/2100MHz AWS wireless band used for its 3G network. Letting go of the idea that there are no other hardware restrictions, we might see a T-Mobile-bound iPhone soon. Apple has nothing to lose, and T-Mobile has everything to gain.

So the question arises: If the iPhone happened to stroll over to T-Mobile, would you make the switch?