T-Mobile (iPhone coming soon teaser)

Earlier today, the nation’s fourth-largest wireless carrier T-Mobile USA annuounced it will start officially selling Apple’s iPhone on April 12. And in dropping annual contracts in favor of monthly installments, the telco unveiled the new Simple Choice Plan and LTE coverage in seven major U.S. cities.

Additional details trickled in post-announcement and one particular tidbit has immediately captured our attention: Apple has actually troubled to re-tool the AT&T iPhone 5 for the Deutsche Telekom-owned carrier.

The re-jigged hardware now supports T-Mobile’s Advanced Wireless Services (AWS) bandwidths, but the change in turn has affected existing AT&T customers who plan on switching to T-Mobile. Full details are right after the break…

First, a little backgrounder.

The Cupertino firm maintains several iPhone hardware versions that cater to the world’s fourth-generation Long-Term Evolution (LTE) flavors, as well as 3G GSM and CDMA standards.

Let me illustrate the LTE fragmentation briefly: prior to today’s announcement, the iPhone 5 used to come in three variants: GSM model A1428 for LTE bands 4 and 17; GSM/CDMA model A1429 for LTE bands 1, 3 and 5; and CDMA variant for China, model A1442 suporting LTE bands 1, 3, 5, 13 and 25.

Now, AWS radios typically use microwave frequencies in two segments: from 1710 to 1755 MHz for uplink, and from 2110 to 2155 MHz for downlink. In the U.S. alone, a few telcos use AWS spectrum, like Big River Broadband, Cincinnati Bell, Mosaic Telecom, Cricket Wireless and of course T-Mobile.

Smaller Canadian providers also use AWS bands. The full list of LTE networks and bandwidths is available on Wikipedia.

iPhone 5 (two-up, front, back, flat)

An Apple representative explained to Engadget it had to re-tool AT&T’s iPhone 5 model A1428 because that device cannot be updated through software to support T-Mobile’s AWS bandwidths.

“Apple affirmed to us that it’s not something that can be enabled via a simple software update for A1428 iPhone units already in circulation,” the publication explains.

An unintended consequence: the current AT&T A1428 iPhone 5 is notably slower on T-Mobile’s network than the re-tooled version Apple made for T-Mobile.

In layman’s terms: existing AT&T customers looking to jump ship are better served buying a brand new iPhone 5 from T-Mobile next month unless, of course, they’re fine with their AT&T iPhone 5 operating slower on T-Mobile’s network due to lack of full AWS support.

AnandTech sheds more light, stating the tweaked A1428 iPhone 5 for T-Mobile is identical hardware to the AT&T A1428 hardware, “it’s just a matter of enabling those modes in the transceiver for WCDMA”.

The re-tooled hardware also supports DC-HSPA+ (42.2 Mbps downlink) on AWS, the publication notes, adding this means “speedy fallback if you detach from LTE and are in a T-Mobile market with two WCDMA carriers.”

Here’s T-Mobile CEO’s “Un-carrier” pitch.

Love that shirt, by the way.

Apple confirmed to Engadget that its online store and 24-hour locations will start carrying the re-tooled A1428 SIM-unlocked on April 12 at 12:01 AM so “eager jetsetters that are simply looking for a frictionless way to purchase an unlocked iPhone 5 that works on both AT&T and T-Mobile’s LTE bands have but a few weeks to wait.”

And should your credit clear, Apple will also support T-Mobile’s $99.99 upfront price on its web store.

Wrapping up, all A1428 iPhone 5 devices, including those sold by AT&T, should be AWS compatible on or until a little bit after April 12.

Again, these new A1428 units will work on both T-Mobile’s and AT&T’s LTE at full speeds (in addition to supporting a bunch of LTE bands around the world) – though the pesky problem of AT&T’s strict unlocking policy still persist.

T-Mobile iPhone FCC testing

By the way, under T-Mobile’s new terms of business both the iPhone 5 and other devices remain locked to its network until it’s fully paid for through monthly installments, at which point the wireless company will happily apply the unlock.

On a final note, the U.S. Federal Communications Commission (FCC) has now cleared the new A1428 iPhone 5 model for the T-Mobile network, complete with AWS support.

Check out the re-jigged hardware being put through its paces at FCC labs in the above photo.

So, are you planning to switch to T-Mobile and support its “Un-carrier” initiative?