Innovators in the wireless world got a cautionary reminder last week that early adopters often end up with arrows in their backs. WiMAX, an upstart wireless-communications technology that has been hyped to high heaven, received its first serious setback. The technology’s two leading proponents scrapped an agreement that would have given America’s mobile-phone companies a run for their money.

Sprint Nextel, America’s third-largest mobile carrier, and its spectrum-aggregation partner, Clearwire, claim the breakup won’t affect their individual plans to build networks in major metropolitan areas. Sprint’s advanced trials in Chicago and the Baltimore/Washington conurbation will doubtless continue.

With investors losing patience with Sprint’s lacklustre performance in its mainstream mobile business, the chief executive, Gary Forsee, was sent packing. With him went some of Sprint’s enthusiasm for WiMAX.

Sprint was stumping up $5 billion to build a network of radio towers for its new WiMAX service, called Xohm. Clearwire brought an attractive chunk of wireless spectrum to the table. Back in July, the two companies agreed to share the cost of delivering high-speed WiMAX connections to 100m users by the end of 2008. Clearwire is now scrambling to find other deep-pocketed partners.

Intel has been an enthusiastic backer of the technology, and is bent on getting its WiMAX-enabled Montevina chips into next year’s crop of laptops and mobile devices. Motorola is another fan. It wants to supply much of the transmission equipment and handsets that connect to WiMAX networks. So do Samsung, Nortel and Alcatel-Lucent. Meanwhile, Google—with its internet heritage and determination to crack open the moribund mobile phone market—could yet prove to be Clearwire’s fairy godmother.

Such firms believe WiMAX is the kind of revolutionary technology that comes along once a decade at most. They expect it to change the world of mobile communications in much the same way as broadband cable and DSL replaced dial-up internet access and ushered in a whole new generation of web services.

What makes WiMAX so special? Think of it as WiFi’s big brother. But where a wireless network in a home, hotel lobby, airport lounge or coffee shop can provide reliable wireless connections at speeds of one or two megabits per second over distances of a few hundred feet, WiMAX is good for at least 10 megabits per second over five miles or more. Better still, in its latest guise, WiMAX can “hand off” connections from one radio tower to the next as users roam around—just like a cellular network.

WiMAX can thus fill the gaps in internet coverage, especially in rural areas and developing countries, where laying cables or telephone lines is too expensive. WiMAX can also provide internet access to mobile users from nearly anywhere. That opens up a whole new market for mobile carriers as well as for makers of internet-access equipment and suppliers of web services.

But WiMAX is not just for people on the move or in remote places. It can also provide internet connectivity to all sorts of devices. Intel wants to put its cheap WiMAX chips in traffic lights, surveillance cameras, television sets and medical equipment. Expect to see them also in digital cameras, iPods and dozens of other portable gizmos.

And those are just the stationary examples. Because the internet until now has been immobile, it has been difficult to imagine applications that take advantage of an internet that goes along for the ride. Clearly, cars are destined to gain internet access—as much for their own use as for the passengers’ sake.

Built from the ground up on internet principles, WiMAX also works seamlessly with the galaxy of internet services developed over the past decade—web surfing, social networking, instant messaging, e-mailing, video streaming, music downloading and, of course, making VOIP (voice over internet protocol) phone calls for free.

Getting cellular networks to perform similar feats, while not impossible, is tricky and expensive. Indeed, with its higher speed, simpler architecture, cheaper equipment, and smarter handling of data, the technology’s boosters expect WiMAX to render the 3G (third-generation) cellular networks that the mobile-phone companies are currently building obsolete over night.

That’s pushing the hype a bit. But the mobile carriers certainly need to show some uncharacteristic haste if they’re to prevent WiMAX from eating at least some of their lunch.

One cellular manufacturer that’s taken the initiative is Ericsson. While not a mobile carrier itself, the Swedish company makes cellular-network equipment and supplies phones to carriers through its partnership with Sony. Ericsson has also had a big hand in developing various 3G technologies in Europe, especially the LTE (long-term evolution) standard. The company expects LTE—an evolution of Europe’s UMTS (universal mobile telecommunications system)—to be more than a match for WiMAX.

In theory, LTE should be able to download data at a scorching 100 megabits per second over short distances, compared with WiMAX’s maximum of 70 megabits per second. Both are effectively 4G, rather than 3G, networks. Either would make watching TV on a mobile device a serious proposition.

Overall, however, two things tip the balance in WiMAX’s favour. One concerns the technology’s origins. Because WiMAX was conceived primarily as a means for internet access rather than as a cellular replacement, it adheres strictly to the internet’s open-standards approach. That means it will work with any internet-ready appliance, no matter the maker or service provider.

In the closed world of cellular networks, appliances tend to be “locked” to a phone company’s proprietary network, and users are limited to just those services and applications their carrier has chosen to offer. In America, subscribers have to buy a new phone whenever they change carriers. The SIM card used in mobile phones elsewhere allows users to take their handsets with them when they change networks, but that’s about all they can do.

By contrast, open standards and interoperability are WiMAX’s cornerstones. Mobile carriers that embrace such values find they have a killer proposition to offer customers. That’s what Sprint’s Mr Forsee was trying to do before being booted out.

The other factor in WiMAX’s favour is its popularity with infrastructure providers. Intel is ramping up production of its Montevina chips (also known as the Centrino Duo) in a bid to find the next billion users for its devices. Motorola is doing the same with WiMAX modems, PC cards and multimode phones.

To cash in on the experience gained from building the world’s first WiMAX network (actually a close relation called WiBro) in South Korea, Samsung is preparing a string of cutting-edge products, including WiMAX-enabled laptops and phones to pocket-sized PCs.

The good news is that at least the hot air surrounding WiMAX is finally giving way to hard silicon. If Sprint, Clearwire and other WiMAX carriers around the globe continue to embrace the openness of the technology, they could find millions of new users—and, in the process, help save the cellular industry from itself.