“We are giving a decade worth of pre-warning,” Khurjekar told Fierce. But even 2021 may be too soon. A Verizon Wireless spokesperson clarified with Fierce that that 2021 is the year to which Verizon is committing to keep its 2G and 3G online so its enterprise and M2M customers can make long-term plans. Verizon has set no firm timeline for shuttering its CDMA network at all, and will continue to offer 2G and 3G as long as it customers want it.

Verizon’s 2G/3G coverage is in red. Its LTE markets are in yellow.

The rest of the mobile industry sees a bit more urgency. AT&T has said it would shut down its 2G network by 2017. It’s already started repurposing old GSM spectrum for HSPA, and there are signs that it is considering a LTE launch in its 2G cellular and PCS frequencies as well. Sprint is finally shutting down Nextel’s old 2G network, refarming its frequencies for 4G. Meanwhile, T-Mobile has lopped off most of its GSM capacity to clear room for more HSPA+ and a new LTE service.

Why isn’t Verizon in a hurry to cannibalize its older technologies as well? For one, Verizon is in the best 4G LTE position of all of the Big 4 operators. After scooping up a bunch of 4G licenses from the cable companies, Big Red has the airwaves to launch a new nationwide LTE network parallel to the one its already deployed.

Also, even if Verizon doesn’t shut down 2G and 3G sites for another nine years, there’s nothing stopping it from whittling away at them. Verizon’s CDMA 1X and EV-DO technologies can persist on very little bandwidth, meaning Verizon could keep nationwide 2G and 3G networks with only a handful of megahertz. It could then take the rest of its cellular and PCS spectrum and put it to 4G use.

Verizon will have to keep a modicum of CDMA online for the foreseeable future though. In 10 years our handsets and tablets will have fully completed the jump to 4G, but there will still be CDMA radios embedded in cars, shipping containers, industrial equipment and even vending machines and jukeboxes, all of which will need a network to link to. Verizon will want to keep those lucrative revenues coming.

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Sprint managed to re-sign 60 percent of those departing Nextel customers to Sprint contracts or to one of its prepaid brands. It also lured 600,000 new subscribers from other carriers with its unlimited iPhone plans and saw more gains from its thriving prepaid and mobile virtual network operator (MVNO) business.

Nextel, which uses iDEN technology rather than the Sprint CDMA network, has been shedding customers for years, but in the second quarter that trend accelerated when Sprint announced it would sunset the aging network in 2013 and stopped selling new iDEN phones. Sprint has already taken 9,600 iDEN sites off air, thinning its network capacity by a third while still maintaining its original coverage footprint, Sprint Network Operations and Wholesale President Steve Elfman said at the company’s earnings call Thursday.

Consequently, 688,000 Nextel and 310,000 Boost subscribers tossed their iDEN phones to curb in the quarter. CEO Dan Hesse said it is much cheaper for Sprint to convert an iDEN customer to CDMA customer than it is to acquire a new customer from a competitor. That led Sprint to focus its marketing spending in the second quarter on moving Nextel subscribers onto Sprint contracts. Of Sprint’s 442,000 new contract CDMA customers in the quarter, 431,000 were former Nextel customers. In addition, of its 451,000 new prepaid customers, 143,000 traded iDEN for CDMA. Hesse, however, warned that Sprint doesn’t expect that high rate of conversion to continue.

The iPhone was also a growth driver for Sprint. It sold 1.5 million iPhone 4 and 4S devices in the quarter, but most significantly, 40 percent of those activations were new customers to Sprint. Though AT&T and Verizon Wireless sold many more iPhones during the quarter, Sprint didn’t experience the same seasonal dip in sales as its competitors — it sold 1.5 million iPhones in the first quarter as well. While consumers aren’t exactly flocking to Sprint’s unlimited iPhone plans in droves, the device coupled with its liberal data pricing is proving to be a steady customer lure.

Sprint also added 388,000 wholesale and affiliate customers, mainly from its MVNO deals. Sprint has become a big destination for virtual operators attracted by its more flexible pricing policies and willingness to share all of its services, including LTE. Though Sprint only receives a fraction of the revenue from a wholesale customer as it would from a contract customer, MVNOs account for a big part of its business — of its 56.4 million total connections, 8.4 million, or 15 percent, are maintained by carrier partners.

Sprint only launched its LTE network this month so it hasn’t started reporting LTE subscribers. Sprint started selling LTE phones long before the network went live and has already seeded the market with four smartphones and a modem. The network is only up in five major metro markets and in 10 additional communities, so as of now relatively few LTE device owners have access to 4G speeds. But Sprint is moving quickly. It plans to expand its footprint to 250,000 million people by the end of 2013.

Photo courtesy of Shutterstock user Susan Law Cain

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Sprint said it has already stopped selling some Nextel devices, and in the next few months it will discontinue its iDEN phone portfolio completely. In two days it will send out notices to its core government and business customers warning them of the pending deadline, and it said it will work with all of its Nextel and Boost Mobile iDEN customers to transition them over to its CDMA network, over which it has recreated the walk-talkie-style Direct Connect service.

Though Sprint may keep the iDEN systems going after the deadline if the migration to CDMA is slower than it anticipates, it probably won’t take too long to fully sunset the network since it has big plans for the spectrum it uses. Sprint wants to launch additional CDMA and LTE systems over iDEN’s 800 MHz spectrum. On Friday, it received permission from the Federal Communications Commission to use those frequencies for LTE, which was the carrier’s final obstacle to refarming its Nextel airwaves for 4G in 2014.

Sprint is already shutting down Nextel sites in several markets, though it is mainly culling cities of excess capacity, not turning off the network completely. It has launched a mapping tool that shows customers which sites are scheduled for decommissioning and when.

Image courtesy of Nikhil Verma.

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That means AT&T is expanding its HSPA network — which it calls 4G – to account for the increasing data load the iPhone and other 3G smartphones are placing on its mobile broadband infrastructure. AT&T runs LTE in NYC, as well, but in a different band. Meanwhile, the backbone of its HSPA service already rides over its PCS frequencies.

In March, AT&T started contacting customers with 2G only phones – specifically very old models that worked only on AT&T’s PCS frequencies – offering them free 3G replacements. AT&T isn’t shutting off 2G completely. It runs a considerable portion of its GSM network at the cellular frequency band, which all phones sold in recent years support. But if AT&T is trying to cull its subscriber base of PCS-only 2G phones, it’s a good sign it plans to shut down GSM at PCS entirely, reserving that band entirely for HSPA.

NYC is AT&T’s densest market so it’s the logical place to start. Unlike the its CDMA 3G counterpart, HSPA supports voice as well as data, so AT&T really isn’t sacrificing any voice capacity. It gains the benefits of a far faster and more efficient mobile broadband network that puts GSM/EDGE sub-megabit speeds to shame. AT&T also may be working with its 3G vendors Ericsson and Alcatel-Lucent to use new configurable bandwidth technologies to gradually shift GSM capacity to HSPA, as opposed to shutting off a huge chunk of its 2G network at once.

Refarming has become a popular trend among U.S. carriers in the last year. T-Mobile is shutting down a large portion of its GSM network to make room for a nationwide LTE rollout and more HSPA capacity. Meanwhile, Sprint plans to retire its Nextel iDEN network by 2014 in order to reuse its 800 MHz frequencies for CDMA and LTE.

Image courtesy of Flickr user joey.parsons

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Speaking at an event at Sprint’s corporate HQ in Overland Park, Kan., Elfman said that the 800 MHz spectrum the iDEN network uses has already been named an official LTE band by the 4G standards powers, and Sprint fully expects to get Federal Communications Commission approval shortly to use the frequencies for 4G, according to Fierce. The only thing left for it to do is to shut down the old Nextel network.

iDEN is ideal for the walkie-talkie-style push-to-talk services that made Nextel so popular circa mid-2000, but it’s awful for delivering data services, which is the direction the wireless industry is charging toward with wild abandon. So Sprint’s answer is to move its push-to-talk over to its LTE CDMA data networks, shut down iDEN and harvest its frequencies for more LTE networks.

The process has already begun. Sprint has started scrapping iDEN base stations and towers in many markets, basically weeding out extra capacity as it continues to shed Nextel customers. It’s even begun posting site-by-site maps of the sunsetting process.

The major take-down work won’t begin until 2013, at which point Sprint will begin a wholesale conversion of its iDEN push-to-talk customers to CDMA and LTE, and start shutting down the Nextel service in whole cities. And as it revealed Thursday, in 2014 it will begin filling up those dormant 800 MHz airwaves with LTE.

Sprint won’t get an enormous amount of capacity out of the Nextel band. It owns an average of 18 MHz nationwide, plus the odd configuration of the band may mean it won’t be use all of its frequencies for LTE. But any bit will help. The LTE network Sprint is deploying this summer over its PCS frequencies measure only 10 MHz in width, compared to the 20 MHz used by Verizon and most of AT&Ts’ 4G systems.

Plus, Ma Bell and Big Red have a lot of unencumbered spectrum to expand their 4G networks into, while Sprint will be forced to cannibalize its CDMA systems to get more LTE capacity. But Sprint is counting on getting a big boost in 2013 when its current mobile broadband provider, Clearwire, hopes to turn on its own LTE network, supplying Sprint with reams of cheap bandwidth. The only drawback with that plan is that Clearwire, so far, only plans to launch LTE in its current limited WiMAX footprint.

Sprint has revealed only a few of its LTE launch markets, but blog Sprint 4G Rollout Updates has gained access to plenty of proprietary information about the full extent of Sprint’s Network Vision plans and has even identified the first 47 cities scheduled to receive the 4G upgrade this year.

Image courtesy Flickr user radialmonster

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Sprint's iDEN network in New Orleans. The dark towers are slated for decommissioning

According to 4G Rollout, New Orleans is the first market on the list with its initial cell sites scheduled to go offline in February shortly after Mardi Gras. Sprint is going to gradually phasing out iDEN so New Orleans Boost and Nextel customers won’t emerge from Fat Tuesday hangovers with no service. But Sprint will pack up its base stations at multiple towers, while expanding nearby cells to fill the gaps.

The iDEN network is actually over-built, designed before the Sprint’s purchase of Nextel and the ensuing flight of millions of customers from its data-impaired networks. So there’s plenty of capacity left in Nextel’s urban networks to cope with a topological rescaling. However, any time you do this kind of network tinkering there will always be coverage holes. Some Nextel and Boost customers can expect their service to suffer, especially as Sprint gets into 2013 and starts shutting down sites en masse.

Outside of New Orleans, there’s not too much useful information since Sprint doesn’t appear to have identified any other specific cell sites scheduled for decommissioning. But you can click on individual sites in your city or town to see when Sprint plans to start its evaluation. For instance, in my city Chicago, all of the sites will likely be under review in June.

Sprint plans to use iDEN’s 800 MHz spectrum for supplemental capacity on its LTE network, which will launch mid-year. But the way Sprint is winnowing down iDEN that spectrum won’t be available until the full network goes dark. Sprint may be shutting down sites, but it’s still using the spectrum. It’s just covering more ground with fewer towers.

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