As with many of its recent expansions, Sprint’s latest rollout encompasses a handful of bigger cities and a bunch of smaller ones. Here’s the complete list of additional markets: Baton Rouge, La.; Centralia, Wash.; Clarksville, Tenn.; Corsicana, Texas; Dalton, Ga.; Dunn, N.C.; Fond du Lac, Wis.; Gainesville, Fla.; Henderson, N.C.; Kingsport, Tenn.; Lansing/East Lansing, Mich.; Longview, Wash.; Napa, Calif.; Palatka, Fla.; Raleigh, N.C.; Sebring, Fla.; St. Cloud, Minn.; St. Joseph/Benton Harbor, Mich.; and Warsaw, Ind.

Sprint’s LTE network is now in a total of 110 markets, though it hasn’t released any figures on the total population covered (it’s target is 200 million people by year end). It still has some noticeable metropolitan holes to fill, including New York City, San Francisco, and Washington, D.C. Though none of those three has officially gone live, Sprint appears to be rapidly completing its Network Vision overhaul in those markets. Customers are already reporting LTE sightings in all three.

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T-Mobile, though, has been short on specifics, so far keeping mum on what particular tweaks it plans to make that will beat out its rivals. But talking to T-Mobile’s equipment vendors, GigaOM has learned some of those details of its network roadmap. The most impressive upgrade on its list is a plan to blanket its network with extra antennas in order to achieve significant performance gains.

The smart antenna technique is called 4×2 MIMO (shorthand for Multiple Input-Multiple Output) and T-Mobile will be among the first if not the first global operator to implement it. Those of you familiar with 4G probably have already heard of 2X2 MIMO, which is used in all LTE networks today. It sends the same data transmission over parallel paths from two antennas at the tower, which are then picked up by two antennas at the receiver. 4X2 MIMO actually doubles the number of antennas — and thus the number of transmission paths — at the tower while the number of antennas in the device remains the same.

In English, that means there are a lot more signals flying at your smartphone, and there will be a lot more antennas at the tower to pick up your phone’s generally weaker return signals. That increases your chance of getting a decent link at the edge of a cell’s coverage zone where connection speeds tend to trail off. 4X2 MIMO won’t increase the maximum speed of the network beyond its 50-to 75-Mbps theoretical limits, but it will ensure that customers at the fringes of the network get much better connections.

How much better? Nokia Siemens Networks North American head of technology Petri Hautakangas said that in lab trials, T-Mobile and NSN are seeing speed gains at the cell edge as high as 100 percent on the uplink and anywhere from a 50 percent to 60 percent increase in downlink bandwidth. Simple geometry means overall network gains would be big (the further the distance from the tower the more space is covered). The end result is a big boost in the real-world capacity of the cell — it can support more simultaneous connections while making more of those connections faster and more resilient.

The best news is for T-Mobile’s accountants. Implementing 4X2 MIMO on T-Mobile’s network will require simple software upgrades to Ericsson and NSN’s base stations as well the installation and the mounting of new antennas on T-Mobile’s towers – many of which are already in place. Since 4X2 MIMO is already in the baseline LTE standard, most current generation handsets will automatically support the technique.

As for timing, Hautakangas had to be a little cagey when talking about a customer’s rollout plans. “I can say that in less than 12 months we’ll have a commercial 4X2 MIMO network rolled out with a major U.S. operator,” he said during an interview. NSN has only one Tier 1 radio infrastructure customer in the U.S., and that’s T-Mobile.

I talked to T-Mobile VP of radio network engineering Mark McDiarmid, and while he wouldn’t discuss the specifics of T-Mobile’s network blueprint, he did confirm that 4X2 MIMO was one of the multiple LTE and LTE-Advanced technologies T-Mobile was considering for future use.

“We have a very good handle on what 4X2 MIMO can do for us,” McDiarmid said. “And we’re one of the few that are in a position to use it.”

As for other technologies on T-Mobile’s roadmap, both Ericsson and NSN confirmed that their network gear will support the eventual upgrade to carrier aggregation, the first of a long list of LTE-Advanced techniques (though it’s still a far cry from being LTE-Advanced ready as T-Mobile likes to claim).

Carrier aggregation bonds two disparate LTE bands together creating a super-fast connection. T-Mobile already uses carrier aggregation in its HSPA+ network, which is how it achieves 42 Mbps speeds over what is technically a 3G network.

Again McDiarmid wouldn’t comment on T-Mobile’s specific plans, but he said T-Mobile is weighing the use carrier aggregation in two ways. First, it could glue together different parts of its current LTE network in the Advanced Wireless Service (AWS) band, giving it bigger channels in markets where it doesn’t have contiguous spectrum. Second, when it launches LTE in the PCS band, it could bind together two completely separate frequency bands, creating the mother of all mobile broadband connections.

T-Mobile image courtesy of Flickr user swruler9284

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PhoneArena has gotten hold of three internal T-Mobile screenshots that show MetroPCS will soon start selling two GSM/HSPA+ phones, the Samsung Galaxy Exhibit and the LG Optimus L9, and that customers will be able to bring unlocked GSM devices such as the iPhone to Metro as well. By virtue of using the global GSM standard, T-Mobile can actually start issuing SIM cards to Metro customers, which is exactly what it appears set to do.

T-Mobile screenshot acquired by PhoneArena

To put this in context, AT&T spent years running two separate network operations — which it called Orange and Blue — after Cingular acquired AT&T Wireless. To be fair, T-Mobile isn’t merging its network with Metro’s. It’s shutting Metro’s CDMA systems down completely, harvesting their spectrum for future T-Mobile’s LTE and HSPA+ networks. T-Mobile, however, plans to maintain the MetroPCS brand for prepaid services, so this move represents more an integration of customer management and billing systems than it does a complete integration of operations.

Still, if PhoneArena’s report proves true, it shows T-Mobile is serious about completing its network overhaul as fast as possible. The faster it gets those MetroPCS customers off of CDMA phones, the sooner it can shut down Metro’s networks.

But there’s a definite benefit for Metro customers as well. They get access to much bigger variety of phones, including devices like the iPhone that were never available to them before. They will have to pay full cost for many of those devices, but since Metro is a prepaid carrier, its customers are already accustomed to paying sticker price. Also, previously every new MetroPCS customer had to buy a new phone when they activated their service. GSM allows them to bring old devices to the network.

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The merger will combine the country’s smallest nationwide carrier with its largest regional carrier, giving the new company a total of 42.5 million wireless customers. That’s still not enough to overtake Sprint as the nation’s No. 3, but it will give the new company plenty of spectrum in key markets. T-Mobile has plotted a course that calls for delivering large quantities of mobile data to consumers at cheap prices and with no contracts. That strategy requires T-Mo to lay its hands on all the spectrum it can find.

Though Deutsche Telekom is the one making the buyout offer, T-Mobile will actually become a part of MetroPCS, taking advantage of the U.S. company’s placement on the New York Stock Exchange. DT, however, will own the majority of the shares, and – though we’ve been calling the new merger T-Metro for short – the company will take on the name T-Mobile USA. MetroPCS will live on as a brand in T-Mo’s arsenal.

The deal sailed over regulatory hurdles (the FCC didn’t even bother to vote on it), but it nevertheless suffered a close call when it came before Metro’s shareholders. Institutional investors took exception to what they considered DT’s low-ball offer and threatened to rage a proxy war to derail the deal.

DT at first played the tough guy refusing back down, but as the shareholder meeting approached earlier this month, it got nervous. MetroPCS rescheduled the meeting for this week, while DT proffered up a new terms – lowering the merged company’s debt load and that debt’s interest rates – to make the more attractive. It worked. The deal’s biggest opponent, hedge fund Paulson & Co., lifted its protests.

Once the deal closes, T-Mobile has a long integration process ahead – an ordeal that makes me question whether the merger is worth the trouble. T-Mobile, however, isn’t looking to duct tape together its GSM-based networks and Metro’s CDMA systems. It has something more radical in mind: cannibalizing MetroPCS for its spectrum. While T-Mo will keep the Metro brand and support its existing customers, the regional carrier’s CDMA and LTE networks are goners. T-Mobile plans to incorporate Metro’s spectrum into its ongoing network overhaul, creating very fast and high-capacity LTE and HSPA+ networks.

This post was updated at 9:30 AM Wednesday to add more background details.

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An internal T-Mobile screenshot leaked to TMoNews states that the iOS update will not only authorize the T-Mobile network (T-Mo’s 2G and a portion of its HSPA+ networks are already supported), but will enable Apple’s visual voicemail and MMS features on the carrier as well. Here’s the text of document:

“The T-Mobile Carrier Update is a minor iOS software update that enables official iPhone support by T-Mobile. When installed, the software update enables a handful of capabilities like Visual Voicemail, MMS Settings and Network/Device optimizations that customers do not have access to today. On April 5, the software update will begin being pushed via OTA to all iPhone devices on the T-Mobile network with iOS 6.1.x or higher.”

I asked Apple and was told it isn’t commenting on a rumor, so I suppose we’ll have to wait until Friday to see if an iOS update shows up in iTunes.

Keep in mind that only the North American GSM iPhone 5 model will work on T-Mobile’s LTE systems, which are now live in seven markets, and to connect to T-Mo you must have an unlocked device. All generations of iPhones will work in T-Mobile’s 2G footprint and on its HSPA+ networks in about 50 markets today. The carrier is expanding that HSPA+ support quickly as it undergoes a major network overhaul.

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Bottom line: if you have a North American GSM version of the iPhone 5 — whether you bought it from AT&T or Apple or got it in from Canada – it can connect to T-Mobile’s new LTE network. It just has to be unlocked. So for AT&T customers looking to switch sides, that means you have to finish your contract, and ask your carrier to unlock the device.

The device will also work on T-Mobile’s 3G HSPA+ network (which T-Mobile calls 4G), just not in every city today. T-Mobile is in the process of a big network overhaul that will align all of its networks with the radios in the iPhone and most other AT&T devices. It’s completed the upgrade in about 50 cities covering 142 million people, but other cities are getting converted quickly.

The source of the confusion is over frequencies, which is why we’ve been seeing all of these references to the Advanced Wireless Services (AWS) band. T-Mobile runs two technologies in the AWS band, it’s LTE network and a portion of its HSPA+ network. The iPhone 5 will support LTE in the AWS band, but it won’t support HSPA+ over AWS. The iPhone 5, and all previous versions of the iPhone, will work on its new upgraded HSPA+ systems in the PCS band.

Apple will release a new version of the iPhone 5 next month that will make all of the band differences completely moot. The updated version will support HSPA+ on both AWS and PCS band. It will even be able to access T-Mobile’s dual-carrier 42 Mbps HSPA+ network, which current and older versions of the iPhone cannot.

All of this is probably still extremely confusing so I’ve broken it down into a Q&A, which hopefully will answer any lingering questions.

How do I know if my iPhone will work on T-Mobile’s networks?

For the iPhone 5, check your model number. It must be the A1428, sold by AT&T, the Canadian operators or Apple. Older iPhone models will also work on T-Mobile’s 2G and 3G networks. All of these devices must be unlocked, though, or they’ll be blocked.

How can I be sure I’ll have access to T-Mobile’s LTE and HSPA+ networks?

For LTE, it’s simple. T-Mobile launched LTE in seven markets this week: Baltimore, Houston, Kansas City, Las Vegas, Phoenix, San Jose, and Washington, D.C. New York City is scheduled to come online this summer along with a bunch of other yet unnamed cities.

For HSPA+, it’s a bit more difficult to tell since T-Mobile doesn’t have any kind of map that tracks which markets have HSPA+ running on the PCS band. They make regular updates on their blog and to the media. PCMag has the most the recent list of T-Mo’s 49 iPhone-optimized cities.

As a general rule of thumb, though, if T-Mobile has LTE in your city, then HSPA+ will be in all the right places, too. And if you get a new version of the iPhone 5 next month, it will work on all of T-Mobile’s network.

When will I be able to bring my old iPhone over to T-Mobile? 

You can do it right now if you like. T-Mobile already has millions of iPhones on its network, running over its 2G and 3G services. In order to access LTE though, you’ll have to wait until Apple updates iOS, authorizing the iPhone 5 to use T-Mobile’s network. Apple hasn’t given a date for when this will happen, saying it will come as an over-the-air update.

Will I be able to access dual-carrier HSPA+?

On a current iPhone, the fastest 3G network you’ll have access to is its 21 Mbps single-carrier system, since all of T-Mo’s dual-carriers are in the AWS band. T-Mobile will eventually launch dual-carrier in the PCS band, but that will take some time. It has to close its acquisition of MetroPCS and convert a lot of old GSM networks to 3G first. If you’re set on accessing the dual-carrier network in the near future, then you’ll need to get one of new versions of the iPhone 5.

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Coupled with the markets T-Mobile has already upgraded, it has a new HSPA+ network running in the PCS 1900 MHz in 37 cities, including many of the country’s largest. T-Mobile isn’t updating its coverage figure for the overhauled network, but these new markets will add considerable numbers to its last count of 100 million people covered.

T-Mobile will begin selling the iPhone sometime next year, but in the interim it has been trying to lure customers with unlocked iPhones over to its network. Its biggest obstacle, however, was the fact that its old network configuration could only supply the iPhone with 2G speeds. By relocating its HSPA+ from the Advanced Wireless Service (AWS) to the PCS band, it can now link to the iPhone’s 3G radios, but T-Mobile also clears up space for its LTE launch next year.

Update: Interestingly enough, T-Mobile customers won’t be the only ones benefiting from this upgrade. T-Mobile mobile virtual network operator Solavei said it would take advantage of its wholesaler’s reconfigured network to support the iPhone as well. Like T-Mobile it won’t sell the iPhone, but it will sell a micro or nano-SIM that fits into an unlocked iPhone and allows customers to take advantage of its $49 unlimited voice, text and data plans. Other MVNOs like Straight Talk already offer similar iPhone SIM activations, though they work mainly on AT&T’s HSPA network. Now that the reconfiguration is well underway, expect more MVNOs to start offering iPhone support over the T-Mobile network soon.

Here is the full description of the new upgraded markets from T-Mobile’s blog:

• New York, including The Bronx, Brooklyn, Manhattan, Queens and Staten Island
• Newark, N.J., including the surrounding cities of East Orange, Elizabeth, Jersey City, North Bergen, Paterson and Union City
• Boston and Cambridge, Mass., including the surrounding cities of Amherst, Andover, Arlington, Bedford, Belmont, Billerica, Braintree, Brockton, Brookline, Burlington, Canton, Chelmsford, Chelsea, Chicopee, Dedham, Everett, Framingham, Hadley, Holbrook, Holyoke, Lawrence, Lexington, Lowell, Ludlow, Lynn, Malden, Marblehead, Medford, Melrose, Metheun, Milton, Nahant, Natick, Needham, Newton, Quincy, Reading, Revere, Salem, Saugus, Sommerville, Stoneham, Swampscott, Tewksbury, Wakefield, Walpole, Waltham, Watertown, Weston, Westwood, Weymouth, Wilmington, Winchester, Winthrop and Woburn
• Springfield, Mass.
• Providence, R.I., including the surrounding cities of Cranston, North Providence, Pawtucket and Warren
• Philadelphia
• Detroit and Warren, Mich., including the surrounding cities of Dearborn, Romulus, Royal Oak, Sterling Heights and Troy
• Dallas, including the surrounding cities of Arlington, Carrolton, The Colony, Denton, Farmers Branch, Flower Mound, Frisco, Garland, Grand Prairie, Irving, Lancaster, Lewisville, McKinney, Mesquite, Plano, Richardson, Rowlett and Southlake
• Fort Worth, Texas, including the surrounding cities of Keller and Mansfield
• Austin, Texas including the surrounding city of Round Rock
• San Antonio
• Tampa, Fla., including the surrounding cities of Clearwater, Largo, Safety Harbor, St. Petersburg and Vinoy Park

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“T-Mobile has entered into an agreement with Apple to bring products to market together next year. Additional details will be made available at a later date,” a T-Mobile spokesman said in a statement.

Update: T-Mobile CEO John Legere has confirmed that the iPhone will be among those Apple devices.

That lines up exactly with what we’ve been saying for the last year. T-Mobile’s network isn’t yet ready to support the iPhone or iPad yet, but it will be in the near future when T-Mo completes its network overhaul. And once that overhaul is complete, Apple will jump at the chance. T-Mobile may be the smallest nationwide operator in the U.S. but it still has a customer base larger than population of most countries.

The big question is how far along in its overhaul T-Mobile will be before the Apple deigns it iPhone ready. In the next six months T-Mobile will likely complete the reconfiguration of HSPA+ on the 1900 MHz PCS band, which will make its 3G network iPhone compatible nationwide (today only its 2G service works on the iPhone). Or Apple may want to wait for T-Mobile’s LTE network, which the carrier plans to launch in the latter half of 2013. If Apple does wait for LTE, that almost certainly means T-Mobile will have to wait for the next generation of iOS devices, whatever they may be.

Either way, once T-Mobile is done with its network upgrades, all generations of the iPhone and iPad will be optimized for its networks, leaving no obstacle for a long and fruitful Apple-T-Mobile relationship.

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T-Mobile’s networks simply aren’t ready yet. The reason T-Mobile has been left off the iPhone bandwagon for so long is that its HSPA networks don’t support the PCS 3G bands the iPhone uses. T-Mobile is fixing that issue, moving its network down the electromagnetic spectrum as part of a nationwide overhaul.

T-Mobile, however, has officially completed that upgrade in only 15 cities. If the iPhone were to go live next week, the vast majority of T-Mobile’s customers who bought it would experience only 2G speeds. That’s to say nothing of the iPhone 5’s LTE capabilities, which T-Mobile won’t support until the second half of 2013. Considering the iPhone is first and foremost a mobile data device, I don’t think even Apple is willing to unleash it on a network that can perform only a fraction of the data functions it was designed for.

Neville Ray, CTO, T-Mobile (c) 2012 Pinar Ozger pinar@pinarozger.com

That said, T-Mobile is aggressively completing its network overhaul, and it has been inviting customers with unlocked iPhones to sign up for SIM-card service. Readers have reported receiving T-Mobile PCS HSPA+ signals all over the country, especially in big metro markets like New York City and Chicago. T-Mo CTO Neville Ray has promised a “material” portion of its footprint will be iPhone-ready by the end of the year.

Make no mistake: the iPhone is bound for T-Mobile. It’s just a question of technology and timing. But unless Ray can somehow complete his nationwide overhaul in the next few weeks, the timing just isn’t right. Logistically that seems impossible, even for network miracle-worker like Ray. In recent weeks, T-Mobile has even tried to distance itself from Apple, claiming the iPhone isn’t necessarily worth the sacrifices.

Who knows? Maybe we’ll hear something from Apple next week about a T-Mobile iPhone, maybe even a commitment to partner with T-Mobile sometime in the future. One of the new iPhone-ready markets T-Mobile announced last week was Apple’s hometown of Cupertino, Calif. You can’t argue with that symbolism. But I wouldn’t hold my breath on getting a magenta iPhone by Christmas.

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KC is only the second city T-Mobile has officially announced as upgraded – Las Vegas was the first – but there has been a lot of activity going on behind the scenes since T-Mo started this process in the summer. Website Airportal.de is keeping a tally of HSPA+ sightings in T-Mobile’s PCS frequencies. The submissions are all unverified, but the map shows activity in dozens of cities from Boston to Los Angeles.

T-Mobile isn’t selling the iPhone, of course, but the carrier has always aggressively recruited iPhone owners to its SIM-card plans. T-Mobile claims to have more than 1 million customers on such bring-your-own-iPhone plans. The problem was, until now, it wasn’t able to offer those customers anything beyond 2G data speeds due to the incompatibility of the iPhone’s 3G radios with the T-Mobile network. With the network overhaul, that all changes.

T-Mobile expects to complete the relocation of its HSPA+ network – which T-Mobile refers to as 4G – in its entire 229-market footprint by mid-2013. After that it will build an LTE network in the spectrum HSPA+ vacated. At that point, T-Mobile also hopes to have closed its merger with MetroPCS, which will give its sizable hunks of new 4G bandwidth in key cities like New York and San Francisco. By the time the overhaul is complete in 2014, T-Mobile’s networks will by in synch with those of the other major North American operators, and hopefully that spells the end of T-Mobile’s long incompatibility with Apple devices.

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