On Friday, Sprint announced that it would deploy a nationwide 4G Long Term Evolution network. The plan: launch service midyear 2012 and by the end of 2013 extend coverage to 250 million people in the U.S. This decision has far-reaching implications, including the further ascendancy of LTE and the relegation of WiMAX to niche status. Previous to this, Sprint's 4G solution was WiMAX, delivered on a network operated by Clearwire. Sprint is a majority owner of Clearwire, along with Clearwire itself, Intel, and Comcast.

WiMAX technology, driven heavily by Intel investment, was intended as a disruptive and superior successor to 3G technologies. Using a wireless approach called Orthogonal Frequency Division Multiple Access (OFDMA), WiMAX promised faster speeds and lower network costs than 3G technologies that were based on Code Division Multiple Access (CDMA). WiMAX has seen some success, primarily in greenfield deployments, with the WiMAX Forum boasting 583 networks in 150 countries. This sounds impressive, but it represents only a tiny percentage of global mobile broadband. Research firm Maravedis anticipates 50 million subscribers by 2015, less than 2% of the 2.96 billion 3G subscribers that Informa predicts.

Clearwire was a big hope for WiMAX investors. With more spectrum available than other wireless operators and with burgeoning mobile-broadband demand, enthusiasts expected it to become the leading 4G wireless technology. But that was not to be, for a number of reasons.

WiMAX looked strong out of the gate. For a while, it was able to position itself as the only 4G technology with a two-year head start. But companies threatened by WiMAX, including Qualcomm and major 3G operators such as AT&T and Verizon, responded aggressively in two ways. First, by participating in enhancements to CDMA-based 3G technologies, and then by accelerating LTE, the "official" cellular industry OFDMA-based 4G technology. This squeezed WiMAX from two sides and limited its window of opportunity. Enhanced 3G, especially High Speed Packet Access Evolved, not only now largely matches WiMAX performance, but HSPA+ operators AT&T and T-Mobile also successfully applied the "4G" label to these technologies, winning over consumers.

Meanwhile, Verizon last year declared it would be the first in the U.S. to have a nationwide LTE network. LTE, a newer technology than WiMax, outperforms WiMAX. Responding to competitive pressure, AT&T also accelerated its own LTE deployment plans. Sprint, which had the most advanced mobile-broadband technology via Clearwire, no longer had that much to show for itself. A slow overall rollout of Clearwire's network didn't help.

Still, Sprint could have stuck with WiMAX, especially since the new version, called WiMAX 2, is faster than today's LTE (though that will be matched by LTE Advanced). But there's just one other problem: scale.

Today's wireless technologies such as LTE are so complex that they consume the entire planetary engineering capability. It’s not just the radio interface. The specifications for LTE cover an entire new network architecture that spans the access network, core network, interworking with other networks, VoIP, quality of service, IPv6, and on and on. If you could somehow envision it, it would be a huge, towering structure in the sky of immense complexity and beauty, one of mankind's greatest creations. Cellular operators globally have chosen LTE. It's only that global scale of hundreds of networks and, eventually, billions of subscribers that makes LTE practical--something an ordinary person can afford to have on a smartphone. That simply cannot be done with another technology, so no other method, no matter how capable, can compete with that. Clearwire itself has announced it will do LTE. However, for various reasons--including having no control over Clearwire--Sprint has decided to do its own LTE network, in conjunction with outsourcing some capacity to LightSquared.

Bottom line, Sprint had no choice--it's jumping on the LTE train before it's too late.

Peter Rysavy is the president of wireless consulting company Rysavy Research and the executive director of the Portable Computer and Communications Association, a nonprofit industry association that addresses key wireless technology developments.

Get lessons from five companies on the front lines of implementing unified communications. Also in the all-digital supplement of Network Computing: Mike Fratto on how to make the case for UC. Download the supplement now. (Free registration required.)

Federal agencies must eliminate 800 data centers over the next five years. Find how they plan to do it in the new all-digital issue of InformationWeek Government. Download it now (registration required).